Maize variety hybrid X18A643

ABSTRACT

A novel maize variety designated X18A643 and seed, plants and plant parts thereof, produced by crossing Pioneer Hi-Bred International, Inc. proprietary inbred maize varieties. Methods for producing a maize plant that comprises crossing hybrid maize variety X18A643 with another maize plant. Methods for producing a maize plant containing in its genetic material one or more traits introgressed into X18A643 through backcross conversion and/or transformation, and to the maize seed, plant and plant part produced thereby. This invention relates to the maize variety X18A643, the seed, the plant produced from the seed, and variants, mutants, and minor modifications of maize variety X18A643. This invention further relates to methods for producing maize varieties derived from maize variety X18A643.

FIELD OF THE INVENTION

This invention relates generally to the field of maize breeding,specifically relating to hybrid maize variety designated X18A643.

BACKGROUND OF THE INVENTION

The goal of hybrid development is to combine, in a single hybrid,various desirable traits. For field crops, these traits may includeresistance to diseases and insects, resistance to heat and drought,reducing the time to crop maturity, greater yield, and better agronomicquality. With mechanical harvesting of many crops, uniformity of plantcharacteristics such as germination, stand establishment, growth rate,maturity, and plant and ear height is important. Traditional plantbreeding is an important tool in developing new and improved commercialcrops.

SUMMARY OF THE INVENTION

According to the invention, there is provided a maize variety, seed,plant, and its parts designated as X18A643, produced by crossing twoPioneer Hi-Bred International, Inc. proprietary maize inbred varieties.This invention relates to the hybrid maize variety X18A643, the seed,the plant and its parts produced from the seed, and variants, mutantsand minor modifications of maize X18A643. This invention also relates toprocesses for making a maize plant containing in its genetic materialone or more traits introgressed into X18A643 through locus conversionand/or transformation, and to the maize seed, plant and plant partsproduced thereby. This invention further relates to methods forproducing maize varieties derived from hybrid maize variety X18A643.

DEFINITIONS

Certain definitions used in the specification are provided below. Alsoin the examples that follow, a number of terms are used herein. In orderto provide a clear and consistent understanding of the specification andclaims, including the scope to be given such terms, the followingdefinitions are provided. NOTE: ABS is in absolute terms and % MN ispercent of the mean for the experiments in which the inbred or hybridwas grown. PCT designates that the trait is calculated as a percentage.% NOT designates the percentage of plants that did not exhibit a trait.For example, STKLDG % NOT is the percentage of plants in a plot thatwere not stalk lodged. These designators will follow the descriptors todenote how the values are to be interpreted. Below are the descriptorsused in the data tables included herein.

ABIOTIC STRESS TOLERANCE: resistance to non-biological sources of stressconferred by traits such as nitrogen utilization efficiency, alterednitrogen responsiveness, drought resistance, cold, and salt resistance

ABTSTK=ARTIFICIAL BRITTLE STALK: A count of the number of “snapped”plants per plot following machine snapping. A snapped plant has itsstalk completely snapped at a node between the base of the plant and thenode above the ear. Expressed as percent of plants that did not snap.

ALLELE: Any of one or more alternative forms of a genetic sequence. In adiploid cell or organism, the two alleles of a given sequence typicallyoccupy corresponding loci on a pair of homologous chromosomes.

ALTER: The utilization of up-regulation, down-regulation, or genesilencing.

ANTHESIS: The time of a flower's opening.

ANTIOXIDANT: A chemical compound or substance that inhibits oxidation,including but not limited to tocopherol or tocotrienols.

ANT ROT=ANTHRACNOSE STALK ROT (Colletotrichum graminicola): A 1 to 9visual rating indicating the resistance to Anthracnose Stalk Rot. Ahigher score indicates a higher resistance. Data are collected only whensufficient selection pressure exists in the experiment measured.

BACKCROSSING: Process in which a breeder crosses a hybrid progenyvariety back to one of the parental genotypes one or more times.

BACKCROSS PROGENY: Progeny plants produced by crossing PHXXX with plantsof another maize line that comprise a desired trait or locus, selectingF1 progeny plants that comprise the desired trait or locus, and crossingthe selected F1 progeny plants with the PHXXX plants 1 or more times toproduce backcross progeny plants that comprise said trait or locus.

BARPLT=BARREN PLANTS: The percent of plants per plot that were notbarren (lack ears).

BLUP indicates BEST LINEAR UNBIASED PREDICTION. The BLUP values aredetermined from a mixed model analysis of hybrid performanceobservations at various locations and replications. BLUP values forinbred maize plants, breeding values, are estimated from the sameanalysis using pedigree information.

BORBMN=ARTIFICIAL BRITTLE STALK MEAN: The mean percent of plants not“snapped” in a plot following artificial selection pressure. A snappedplant has its stalk completely snapped at a node between the base of theplant and the node above the ear. Expressed as percent of plants thatdid not snap. A high number is good and indicates tolerance to brittlesnapping.

BRENGMN=BRITTLE STALK ENERGY MEAN: The mean amount of energy per unitarea needed to artificially brittle snap a corn stalk. A high number isgood and indicates tolerance to brittle snapping.

BREEDING: The genetic manipulation of living organisms.

BREEDING CROSS: A cross to introduce new genetic material into a plantfor the development of a new variety. For example, one could cross plantA with plant B, wherein plant B would be genetically different fromplant A. After the breeding cross, the resulting F1 plants could then beselfed or sibbed for one, two, three or more times (F1, F2, F3, etc.)until a new inbred variety is developed.

BRLPNE=ARTIFICIAL ROOT LODGING EARLY SEASON: The percent of plants notroot lodged in a plot following artificial selection pressure appliedprior to flowering. A plant is considered root lodged if it leans fromthe vertical axis at an approximately 30 degree angle or greater.Expressed as percent of plants that did not root lodge. A high number isgood and indicates tolerance to root lodging.

BRLPNL=ARTIFICIAL ROOT LODGING LATE SEASON: The percent of plants notroot lodged in a plot following artificial selection pressure duringgrain fill. A plant is considered root lodged if it leans from thevertical axis at an approximately 30 degree angle or greater. Expressedas percent of plants that did not root lodge. A high number is good andindicates tolerance to root lodging.

BRTSTK=BRITTLE STALKS: This is a measure of the stalk breakage near thetime of pollination, and is an indication of whether a hybrid or inbredwould snap or break near the time of flowering under severe winds. Dataare presented as percentage of plants that did not snap. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

BRTPCN=BRITTLE STALKS: This is an estimate of the stalk breakage nearthe time of pollination, and is an indication of whether a hybrid orinbred would snap or break near the time of flowering under severewinds. Data are presented as percentage of plants that did not snap.Data are collected only when sufficient selection pressure exists in theexperiment measured.

CARBOHYDRATE: Organic compounds comprising carbon, oxygen and hydrogen,including sugars, starches and cellulose.

CELL: Cell as used herein includes a plant cell, whether isolated, intissue culture or incorporated in a plant or plant part.

CLDTST=COLD TEST: The percent of plants that germinate under cold testconditions.

CLN=CORN LETHAL NECROSIS: Synergistic interaction of maize chloroticmottle virus (MCMV) in combination with either maize dwarf mosaic virus(MDMV-A or MDMV-B) or wheat streak mosaic virus (WSMV). A 1 to 9 visualrating indicating the resistance to Corn Lethal Necrosis. A higher scoreindicates a higher resistance. Data are collected only when sufficientselection pressure exists in the experiment measured.

CMSMT=COMMON SMUT: This is the percentage of plants not infected withCommon Smut. Data are collected only when sufficient selection pressureexists in the experiment measured.

COMRST=COMMON RUST (Puccinia sorghi): A 1 to 9 visual rating indicatingthe resistance to Common Rust. A higher score indicates a higherresistance. Data are collected only when sufficient selection pressureexists in the experiment measured.

CROSS POLLINATION: Fertilization by the union of two gametes fromdifferent plants.

CROSSING: The combination of genetic material by traditional methodssuch as a breeding cross or backcross, but also including protoplastfusion and other molecular biology methods of combining genetic materialfrom two sources.

D/D=DRYDOWN: This represents the relative rate at which a hybrid willreach acceptable harvest moisture compared to other hybrids on a 1 to 9rating scale. A high score indicates a hybrid that dries relatively fastwhile a low score indicates a hybrid that dries slowly.

DIGENG=DIGESTABLE ENERGY: Near-infrared transmission spectroscopy, NIT,prediction of digestible energy.

DIPERS=DIPLODIA EAR MOLD SCORES (Diplodia maydis and Diplodiamacrospora): A 1 to 9 visual rating indicating the resistance toDiplodia Ear Mold. A higher score indicates a higher resistance. Dataare collected only when sufficient selection pressure exists in theexperiment measured.

DIPLOID PLANT PART: Refers to a plant part or cell that has the samediploid genotype as PHXXX.

DIPROT=DIPLODIA STALK ROT SCORE: Score of stalk rot severity due toDiplodia (Diplodia maydis). Expressed as a 1 to 9 score with 9 beinghighly resistant. Data are collected only when sufficient selectionpressure exists in the experiment measured.

DRPEAR=DROPPED EARS: A measure of the number of dropped ears per plotand represents the percentage of plants that did not drop ears prior toharvest. Data are collected only when sufficient selection pressureexists in the experiment measured.

D/T=DROUGHT TOLERANCE: This represents a 1 to 9 rating for droughttolerance, and is based on data obtained under stress conditions. A highscore indicates good drought tolerance and a low score indicates poordrought tolerance. Data are collected only when sufficient selectionpressure exists in the experiment measured.

EARHT=EAR HEIGHT: The ear height is a measure from the ground to thehighest placed developed ear node attachment and is measured in inches.

EARMLD=GENERAL EAR MOLD: Visual rating (1 to 9 score) where a 1 is verysusceptible and a 9 is very resistant. This is based on overall ratingfor ear mold of mature ears without determining the specific moldorganism, and may not be predictive for a specific ear mold. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

EARSZ=EAR SIZE: A 1 to 9 visual rating of ear size. The higher therating the larger the ear size.

EBTSTK=EARLY BRITTLE STALK: A count of the number of “snapped” plantsper plot following severe winds when the corn plant is experiencing veryrapid vegetative growth in the V5-V8 stage. Expressed as percent ofplants that did not snap. Data are collected only when sufficientselection pressure exists in the experiment measured.

ECB1LF=EUROPEAN CORN BORER FIRST GENERATION LEAF FEEDING (Ostrinianubilalis): A 1 to 9 visual rating indicating the resistance topreflowering leaf feeding by first generation European Corn Borer. Ahigher score indicates a higher resistance. Data are collected only whensufficient selection pressure exists in the experiment measured.

ECB21T=EUROPEAN CORN BORER SECOND GENERATION INCHES OF TUNNELING(Ostrinia nubilalis): Average inches of tunneling per plant in thestalk. Data are collected only when sufficient selection pressure existsin the experiment measured.

ECB2SC=EUROPEAN CORN BORER SECOND GENERATION (Ostrinia nubilalis): A 1to 9 visual rating indicating post flowering degree of stalk breakageand other evidence of feeding by second generation European Corn Borer.A higher score indicates a higher resistance. Data are collected onlywhen sufficient selection pressure exists in the experiment measured.

ECBDPE=EUROPEAN CORN BORER DROPPED EARS (Ostrinia nubilalis): Droppedears due to European Corn Borer. Percentage of plants that did not dropears under second generation European Corn Borer infestation. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

ECBLSI=EUROPEAN CORN BORER LATE SEASON INTACT (Ostrinia nubilalis): A 1to 9 visual rating indicating late season intactness of the corn plantgiven damage (stalk breakage above and below the top ear) causedprimarily by 2^(nd) and/or 3^(rd) generation ECB larval feeding beforeharvest. A higher score is good and indicates more intact plants. Dataare collected only when sufficient selection pressure exists in theexperiment measured.

EGRWTH=EARLY GROWTH: This is a measure of the relative height and sizeof a corn seedling at the 2-4 leaf stage of growth. This is a visualrating (1 to 9), with 1 being weak or slow growth, 5 being averagegrowth and 9 being strong growth. Taller plants, wider leaves, moregreen mass and darker color constitute higher score. Data are collectedonly when sufficient selection pressure exists in the experimentmeasured.

ERTLDG=EARLY ROOT LODGING: The percentage of plants that do not rootlodge prior to or around anthesis; plants that lean from the verticalaxis at an approximately 30 degree angle or greater would be counted asroot lodged. Data are collected only when sufficient selection pressureexists in the experiment measured.

ERTLPN=EARLY ROOT LODGING: An estimate of the percentage of plants thatdo not root lodge prior to or around anthesis; plants that lean from thevertical axis at an approximately 30 degree angle or greater would beconsidered as root lodged. Data are collected only when sufficientselection pressure exists in the experiment measured.

ERTLSC=EARLY ROOT LODGING SCORE: Score for severity of plants that leanfrom a vertical axis at an approximate 30 degree angle or greater whichtypically results from strong winds prior to or around floweringrecorded within 2 weeks of a wind event. Expressed as a 1 to 9 scorewith 9 being no lodging. Data are collected only when sufficientselection pressure exists in the experiment measured.

ESSENTIAL AMINO ACIDS: Amino acids that cannot be synthesized de novo byan organism and therefore must be supplied in the diet.

ESTCNT=EARLY STAND COUNT: This is a measure of the stand establishmentin the spring and represents the number of plants that emerge on perplot basis for the inbred or hybrid.

EXPRESSING: Having the genetic potential such that under the rightconditions, the phenotypic trait is present.

EXTSTR=EXTRACTABLE STARCH: Near-infrared transmission spectroscopy, NIT,prediction of extractable starch.

EYESPT=EYE SPOT (Kabatiella zeae or Aureobasidium zeae): A 1 to 9 visualrating indicating the resistance to Eye Spot. A higher score indicates ahigher resistance. Data are collected only when sufficient selectionpressure exists in the experiment measured.

FATTY ACID: A carboxylic acid (or organic acid), often with a longaliphatic tail (long chains), either saturated or unsaturated.

F1 PROGENY: A progeny plant produced by crossing a plant with a plant ofanother maize line.

FUSERS=FUSARIUM EAR ROT SCORE (Fusarium moniliforme or Fusariumsubglutinans): A 1 to 9 visual rating indicating the resistance toFusarium Ear Rot. A higher score indicates a higher resistance. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

GDU=GROWING DEGREE UNITS: Using the Barger Heat Unit Theory, whichassumes that maize growth occurs in the temperature range 50 degreesF.-86 degrees F. and that temperatures outside this range slow downgrowth; the maximum daily heat unit accumulation is 36 and the minimumdaily heat unit accumulation is 0. The seasonal accumulation of GDU is amajor factor in determining maturity zones.

GDUSHD=GDU TO SHED: The number of growing degree units (GDUs) or heatunits required for an inbred variety or hybrid to have approximately 50percent of the plants shedding pollen and is measured from the time ofplanting. Growing degree units are calculated by the Barger Method,where the heat units for a 24-hour period are:

${G\; D\; U} = {\frac{\left( {{Max}.{\mspace{11mu}\;}{temp}.{+ {{Min}.\mspace{14mu}{temp}.}}} \right)}{2} - 50}$

The units determined by the Barger Method are then divided by 10. Thehighest maximum temperature used is 86 degrees F. and the lowest minimumtemperature used is 50 degrees F. For each inbred or hybrid it takes acertain number of GDUs to reach various stages of plant development.

GDUSLK=GDU TO SILK: The number of growing degree units required for aninbred variety or hybrid to have approximately 50 percent of the plantswith silk emergence from time of planting. Growing degree units arecalculated by the Barger Method as given in GDU SHD definition and thendivided by 10.

GENE SILENCING: The interruption or suppression of the expression of agene at the level of transcription or translation.

GENOTYPE: Refers to the genetic constitution of a cell or organism.

GIBERS=GIBBERELLA EAR ROT (PINK MOLD) (Gibberella zeae): A 1 to 9 visualrating indicating the resistance to Gibberella Ear Rot. A higher scoreindicates a higher resistance. Data are collected only when sufficientselection pressure exists in the experiment measured.

GIBROT=GIBBERELLA STALK ROT SCORE: Score of stalk rot severity due toGibberella (Gibberella zeae). Expressed as a 1 to 9 score with 9 beinghighly resistant. Data are collected only when sufficient selectionpressure exists in the experiment measured.

GLFSPT=GRAY LEAF SPOT (Cercospora zeae-maydis): A 1 to 9 visual ratingindicating the resistance to Gray Leaf Spot. A higher score indicates ahigher resistance. Data are collected only when sufficient selectionpressure exists in the experiment measured.

GOSWLT=GOSS' WILT (Corynebacterium nebraskense): A 1 to 9 visual ratingindicating the resistance to Goss' Wilt. A higher score indicates ahigher resistance. Data are collected only when sufficient selectionpressure exists in the experiment measured.

GRNAPP=GRAIN APPEARANCE: This is a 1 to 9 rating for the generalappearance of the shelled grain as it is harvested based on such factorsas the color of harvested grain, any mold on the grain, and any crackedgrain. High scores indicate good grain visual quality.

HAPLOID PLANT PART: Refers to a plant part or cell that has the samehaploid genotype as PHXXX.

HCBLT=HELMINTHOSPORIUM CARBONUM LEAF BLIGHT (Helminthosporium carbonum):A 1 to 9 visual rating indicating the resistance to Helminthosporiuminfection. A higher score indicates a higher resistance. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

HD SMT=HEAD SMUT (Sphacelotheca reiliana): This indicates the percentageof plants not infected. Data are collected only when sufficientselection pressure exists in the experiment measured.

HSKCVR=HUSK COVER: A 1 to 9 score based on performance relative to keychecks, with a score of 1 indicating very short husks, tip of ear andkernels showing; 5 is intermediate coverage of the ear under mostconditions, sometimes with thin husk; and a 9 has husks extending andclosed beyond the tip of the ear. Scoring can best be done nearphysiological maturity stage or any time during dry down untilharvested.

HTFRM=Near-infrared transmission spectroscopy, NIT, prediction offermentables.

HYBRID VARIETY: A substantially heterozygous hybrid line and minorgenetic modifications thereof that retain the overall genetics of thehybrid line including but not limited to a locus conversion, a mutation,or a somoclonal variant.

INBRED: A variety developed through inbreeding or doubled haploidy thatpreferably comprises homozygous alleles at about 95% or more of itsloci.

INC D/A=GROSS INCOME (DOLLARS PER ACRE): Relative income per acreassuming drying costs of two cents per point above 15.5 percent harvestmoisture and current market price per bushel.

INCOME/ACRE: Income advantage of hybrid to be patented over other hybridon per acre basis.

INC ADV=GROSS INCOME ADVANTAGE: Gross income advantage of variety #1over variety #2.

INTROGRESSION: The process of transferring genetic material from onegenotype to another.

KERUNT=KERNELS PER UNIT AREA (Acres or Hectares).

KERPOP=KERNEL POP SCORE: The visual 1-9 rating of the amount ofrupturing of the kernel pericarp at an early stage in grain fill. Ahigher score is good and indicates no popped (ruptured) kernels.

KER_WT=KERNEL NUMBER PER UNIT WEIGHT (Pounds or Kilograms): The numberof kernels in a specific measured weight; determined after removal ofextremely small and large kernels.

KSZDCD=KERNEL SIZE DISCARD: The percent of discard seed; calculated asthe sum of discarded tip kernels and extra large kernels.

LINKAGE: Refers to a phenomenon wherein alleles on the same chromosometend to segregate together more often than expected by chance if theirtransmission was independent.

LINKAGE DISEQUILIBRIUM: Refers to a phenomenon wherein alleles tend toremain together in linkage groups when segregating from parents tooffspring, with a greater frequency than expected from their individualfrequencies.

LOCUS: A specific location on a chromosome.

LOCUS CONVERSION: (Also called TRAIT CONVERSION) A locus conversionrefers to plants within a variety that have been modified in a mannerthat retains the overall genetics of the variety and further comprisesone or more loci with a specific desired trait, such as male sterility,insect, disease or herbicide resistance. Examples of single locusconversions include mutant genes, transgenes and native traits finelymapped to a single locus. One or more locus conversion traits may beintroduced into a single corn variety.

L/POP=YIELD AT LOW DENSITY: Yield ability at relatively low plantdensities on a 1 to 9 relative system with a higher number indicatingthe hybrid responds well to low plant densities for yield relative toother hybrids. A 1, 5, and 9 would represent very poor, average, andvery good yield response, respectively, to low plant density.

LRTLDG=LATE ROOT LODGING: The percentage of plants that do not rootlodge after anthesis through harvest; plants that lean from the verticalaxis at an approximately 30 degree angle or greater would be counted asroot lodged. Data are collected only when sufficient selection pressureexists in the experiment measured.

LRTLPN=LATE ROOT LODGING: An estimate of the percentage of plants thatdo not root lodge after anthesis through harvest; plants that lean fromthe vertical axis at an approximately 30 degree angle or greater wouldbe considered as root lodged. Data are collected only when sufficientselection pressure exists in the experiment measured.

LRTLSC=LATE ROOT LODGING SCORE: Score for severity of plants that leanfrom a vertical axis at an approximate 30 degree angle or greater whichtypically results from strong winds after flowering. Recorded prior toharvest when a root-lodging event has occurred. This lodging results inplants that are leaned or “lodged” over at the base of the plant and donot straighten or “goose-neck” back to a vertical position. Expressed asa 1 to 9 score with 9 being no lodging. Data are collected only whensufficient selection pressure exists in the experiment measured.

MALE STERILITY: A male sterile plant is one which produces no viablepollen no (pollen that is able to fertilize the egg to produce a viableseed). Male sterility prevents self pollination. These male sterileplants are therefore useful in hybrid plant production.

MDMCPX=MAIZE DWARF MOSAIC COMPLEX (MDMV=Maize Dwarf Mosaic Virus andMCDV=Maize Chlorotic Dwarf Virus). A 1 to 9 visual rating indicating theresistance to Maize Dwarf Mosaic Complex. A higher score indicates ahigher resistance. Data are collected only when sufficient selectionpressure exists in the experiment measured.

MILKLN=percent milk in mature grain.

MST=HARVEST MOISTURE: The moisture is the actual percentage moisture ofthe grain at harvest.

MSTADV=MOISTURE ADVANTAGE: The moisture advantage of variety #1 overvariety #2 as calculated by: MOISTURE of variety #2—MOISTURE of variety#1=MOISTURE ADVANTAGE of variety #1.

NEI DISTANCE: A quantitative measure of percent similarity between twovarieties. Nei's distance between varieties A and B can be defined as1-(2*number alleles in common/(number alleles in A+number alleles in B).For example, if varieties A and B are the same for 95 out of 100alleles, the Nei distance would be 0.05. If varieties A and B are thesame for 98 out of 100 alleles, the Nei distance would be 0.02. Freesoftware for calculating Nei distance is available on the internet atmultiple locations such as, for example, at:evolution.genetics.washington.edu/phylip.html. See Nei, Proc Natl AcadSci, 76:5269-5273 (1979) which is incorporated by reference for thispurpose.

NLFBLT=NORTHERN LEAF BLIGHT (Helminthosporium turcicum or Exserohilumturcicum): A 1 to 9 visual rating indicating the resistance to NorthernLeaf Blight. A higher score indicates a higher resistance. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

NUCLEIC ACID: An acidic, chainlike biological macromolecule consistingof multiple repeat units of phosphoric acid, sugar and purine andpyrimidine bases.

OILT=GRAIN OIL: Absolute value of oil content of the kernel as predictedby Near-Infrared Transmittance and expressed as a percent of dry matter.

PERCENT IDENTITY: Percent identity as used herein refers to thecomparison of the alleles present in two varieties. For example, whencomparing two inbred plants to each other, each inbred plant will havethe same allele (and therefore be homozygous) at almost all of theirloci. Percent identity is determined by comparing a statisticallysignificant number of the homozygous alleles of two varieties. Forexample, a percent identity of 90% between X18A643 and other varietymeans that the two varieties have the same homozygous alleles at 90% oftheir loci.

PLANT: As used herein, the term “plant” includes reference to animmature or mature whole plant, including a plant that has beendetasseled or from which seed or grain has been removed. Seed or embryothat will produce the plant is also considered to be the plant.

PLANT PART: As used herein, the term “plant part” includes leaves,stems, roots, seed, grain, embryo, pollen, ovules, flowers, ears, cobs,husks, stalks, root tips, anthers, pericarp, silk, tissue, cells and thelike.

PLATFORM indicates the variety with the base genetics and the varietywith the base genetics comprising locus conversion(s). There can be aplatform for the inbred maize variety and the hybrid maize variety.

PLTHT=PLANT HEIGHT: This is a measure of the height of the plant fromthe ground to the tip of the tassel in inches.

POLPRD=POLLEN PRODUCTION SCORE: The estimated total amount of pollenproduced by tassels based on the number of tassel branches and thedensity of the spikelets.

POLSC=POLLEN SCORE: A 1 to 9 visual rating indicating the amount ofpollen shed. The higher the score the more pollen shed.

POLWT=POLLEN WEIGHT: This is calculated by dry weight of tasselscollected as shedding commences minus dry weight from similar tasselsharvested after shedding is complete.

POP K/A=PLANT POPULATIONS: Measured as 1000's per acre.

POP ADV=PLANT POPULATION ADVANTAGE: The plant population advantage ofvariety #1 over variety #2 as calculated by PLANT POPULATION of variety#2—PLANT POPULATION of variety #1=PLANT POPULATION ADVANTAGE of variety#1.

PRM=PREDICTED RELATIVE MATURITY: This trait, predicted relativematurity, is based on the harvest moisture of the grain. The relativematurity rating is based on a known set of checks and utilizes standardlinear regression analyses and is also referred to as the ComparativeRelative Maturity Rating System that is similar to the MinnesotaRelative Maturity Rating System.

PRMSHD: A relative measure of the growing degree units (GDU) required toreach 50% pollen shed. Relative values are predicted values from thelinear regression of observed GDU's on relative maturity of commercialchecks.

PROT=GRAIN PROTEIN: Absolute value of protein content of the kernel aspredicted by Near-Infrared Transmittance and expressed as a percent ofdry matter.

RESISTANCE: Synonymous with tolerance. The ability of a plant towithstand exposure to an insect, disease, herbicide or other condition.A resistant plant variety will have a level of resistance higher than acomparable wild-type variety.

RTLDG=ROOT LODGING: Root lodging is the percentage of plants that do notroot lodge; plants that lean from the vertical axis at an approximately30 degree angle or greater would be counted as root lodged. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

RTLADV=ROOT LODGING ADVANTAGE: The root lodging advantage of variety #1over variety #2. Data are collected only when sufficient selectionpressure exists in the experiment measured.

SCTGRN=SCATTER GRAIN: A 1 to 9 visual rating indicating the amount ofscatter grain (lack of pollination or kernel abortion) on the ear. Thehigher the score the less scatter grain.

SDGVGR=SEEDLING VIGOR: This is the visual rating (1 to 9) of the amountof vegetative growth after emergence at the seedling stage(approximately five leaves). A higher score indicates better vigor.

SEED: Fertilized and ripened ovule, consisting of the plant embryo,varying amounts of stored food material, and a protective outer seedcoat. Synonymous with grain.

SEFIELD: Percent stress emergence in field.

SELAB: Average % stress emergence in lab tests.

SEL IND=SELECTION INDEX: The selection index gives a single measure ofthe hybrid's worth based on information for multiple traits. A maizebreeder may utilize his or her own set of traits for the selectionindex. One of the traits that is almost always included is yield. Theselection index data presented in the tables represent the mean valueaveraged across testing stations.

SELF POLLINATION: A plant is self-pollinated if pollen from one floweris transferred to the same or another flower of the same plant.

SIB POLLINATION: A plant is sib-pollinated when individuals within thesame family or variety are used for pollination.

SITE SPECIFIC INTEGRATION: Genes that create a site for site specificDNA integration. This includes the introduction of FRT sites that may beused in the FLP/FRT system and/or Lox sites that may be used in theCre/Loxp system. For example, see Lyznik, et al., Site-SpecificRecombination for Genetic Engineering in Plants, Plant Cell Rep (2003)21:925-932 and WO 99/25821.

SLFBLT=SOUTHERN LEAF BLIGHT (Helminthosporium maydis or Bipolarismaydis): A 1 to 9 visual rating indicating the resistance to SouthernLeaf Blight. A higher score indicates a higher resistance. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

SOURST=SOUTHERN RUST (Puccinia polysora): A 1 to 9 visual ratingindicating the resistance to Southern Rust. A higher score indicates ahigher resistance. Data are collected only when sufficient selectionpressure exists in the experiment measured.

SPKDSC=SPIKLET DENSITY SCORE: The visual 1-9 rating of how densespikelets are on the middle tassel branches. A higher score indicateshigher spikelet density.

STAGRN=STAY GREEN: Stay green is the measure of plant health near thetime of black layer formation (physiological maturity). A high scoreindicates better late-season plant health.

STDADV=STALK STANDING ADVANTAGE: The advantage of variety #1 overvariety #2 for the trait STKCNT.

STKCNT=NUMBER OF PLANTS: This is the final stand or number of plants perplot.

STKCTE: This is the early stand count of plants per plot.

STKLDG=STALK LODGING REGULAR: This is the percentage of plants that didnot stalk lodge (stalk breakage) at regular harvest (when grain moistureis between about 20 and 30%) as measured by either natural lodging orpushing the stalks and determining the percentage of plants that breakbelow the ear. Data are collected only when sufficient selectionpressure exists in the experiment measured.

STKLDS=STALK LODGING SCORE: A plant is considered as stalk lodged if thestalk is broken or crimped between the ear and the ground. This can becaused by any or a combination of the following: strong winds late inthe season, disease pressure within the stalks, ECB damage orgenetically weak stalks. This trait should be taken just prior to or atharvest. Expressed on a 1 to 9 scale with 9 being no lodging. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

STLLPN=LATE STALK LODGING: This is the percent of plants that did notstalk lodge (stalk breakage or crimping) at or around late seasonharvest (when grain moisture is below 20%) as measured by either naturallodging or pushing the stalks and determining the percentage of plantsthat break or crimp below the ear. Data are collected only whensufficient selection pressure exists in the experiment measured.

STLPCN=STALK LODGING REGULAR: This is an estimate of the percentage ofplants that did not stalk lodge (stalk breakage) at regular harvest(when grain moisture is between about 20 and 30%) as measured by eithernatural lodging or pushing the stalks and determining the percentage ofplants that break below the ear. Data are collected only when sufficientselection pressure exists in the experiment measured.

STLTIP=STERILE TIPS SCORE: The visual 1 to 9 rating of the relative lackof glumes on the tassel central spike and branches. A higher scoreindicates less incidence of sterile tips or lack of glumes on thetassel.

STRT=GRAIN STARCH: Absolute value of starch content of the kernel aspredicted by Near-Infrared Transmittance and expressed as a percent ofdry matter.

STWWLT=Stewart's Wilt (Erwinia stewartii): A 1 to 9 visual ratingindicating the resistance to Stewart's Wilt. A higher score indicates ahigher resistance. Data are collected only when sufficient selectionpressure exists in the experiment measured.

SSRs: Genetic markers based on polymorphisms in repeated nucleotidesequences, such as microsatellites. A marker system based on SSRs can behighly informative in linkage analysis relative to other marker systemsin that multiple alleles may be present.

TASBLS=TASSEL BLAST: A 1 to 9 visual rating was used to measure thedegree of blasting (necrosis due to heat stress) of the tassel at thetime of flowering. A 1 would indicate a very high level of blasting attime of flowering, while a 9 would have no tassel blasting. Data arecollected only when sufficient selection pressure exists in theexperiment measured.

TASBRN=TASSEL BRANCH NUMBER: The number of tassel branches, with anthersoriginating from the central spike.

TASSZ=TASSEL SIZE: A 1 to 9 visual rating was used to indicate therelative size of the tassel. The higher the rating the larger thetassel.

TAS WT=TASSEL WEIGHT: This is the average weight of a tassel (grams)just prior to pollen shed.

TEXEAR=EAR TEXTURE: A 1 to 9 visual rating was used to indicate therelative hardness (smoothness of crown) of mature grain. A 1 would bevery soft (extreme dent) while a 9 would be very hard (flinty or verysmooth crown).

TILLER=TILLERS: A count of the number of tillers per plot that couldpossibly shed pollen was taken. Data are given as a percentage oftillers: number of tillers per plot divided by number of plants perplot. A tiller is defined as a secondary shoot that has developed as atassel capable of shedding pollen.

TSTWT=TEST WEIGHT (ADJUSTED): The measure of the weight of the grain inpounds for a given volume (bushel), adjusted for MST less than or equalto 22 percent.

TSTWTN=TEST WEIGHT (UNADJUSTED): The measure of the weight of the grainin pounds for a given volume (bushel).

TSWADV=TEST WEIGHT ADVANTAGE: The test weight advantage of variety #1over variety #2.

VARIETY: A maize line and minor genetic modifications thereof thatretain the overall genetics of the line including but not limited to alocus conversion, a mutation, or a somoclonal variant.

WIN M %=PERCENT MOISTURE WINS.

WIN Y %=PERCENT YIELD WINS.

YIELD BU/A=YIELD (BUSHELS/ACRE): Yield of the grain at harvest by weightor volume (bushels) per unit area (acre) adjusted to 15% moisture.

YLDADV=YIELD ADVANTAGE: The yield advantage of variety #1 over variety#2 as calculated by: YIELD of variety #1—YIELD variety #2=YIELDADVANTAGE of variety #1.

YIELDMST=YIELD/MOISTURE RATIO.

YLDSC=YIELD SCORE: A 1 to 9 visual rating was used to give a relativerating for yield based on plot ear piles. The higher the rating thegreater visual yield appearance.

When referring to area of adaptability, such term is used to describethe location with the environmental conditions that would be well suitedfor this maize variety. Area of adaptability is based on a number offactors, for example: days to maturity, insect resistance, diseaseresistance, and drought resistance. Area of adaptability does notindicate that the maize variety will grow in every location within thearea of adaptability or that it will not grow outside the area.

DETAILED DESCRIPTION OF THE INVENTION AND FURTHER EMBODIMENTS

All tables discussed in the Detailed Description of the Invention andFurther Embodiments section can be found at the end of the section.

Field crops are bred through techniques that take advantage of theplant's method of pollination. A plant is self-pollinated if pollen fromone flower is transferred to the same or another flower of the sameplant. A plant is sib pollinated when individuals within the same familyor line are used for pollination. A plant is cross-pollinated if thepollen comes from a flower on a different plant from a different familyor line.

Plants that have been self-pollinated and selected for type for manygenerations become homozygous at almost all gene loci and produce auniform population of true breeding progeny. A cross between twodifferent homozygous lines produces a uniform population of hybridplants that may be heterozygous for many gene loci. A cross of twoplants each heterozygous at a number of gene loci will produce apopulation of heterogeneous plants that differ genetically and will notbe uniform.

Maize (Zea mays L.), often referred to as corn in the United States, canbe bred by both self-pollination and cross-pollination techniques. Maizehas separate male and female flowers on the same plant, located on thetassel and the ear, respectively. Natural pollination occurs in maizewhen wind blows pollen from the tassels to the silks that protrude fromthe tops of the ears.

There are many important factors to be considered in the art of plantbreeding, such as the ability to recognize important characteristics,the ability to design evaluation techniques for genotypic and phenotypictraits of interest, and the ability to search out and exploit the genesfor the desired traits in new or improved combinations.

One objective of commercial maize variety development is to producehybrids with high grain yields and superior agronomic performance. Oneof the primary traits breeders seek is yield. However, many other majoragronomic traits are of importance in hybrid combination and have animpact on yield or otherwise provide superior performance in hybridcombinations. Such traits include percent grain moisture at harvest,relative maturity, resistance to stalk breakage, resistance to rootlodging, grain quality, and disease and insect resistance.

Phenotypic Characteristics of X18A643

Pioneer Brand Hybrid Maize Variety X18A643 is a single cross, yellowendosperm maize variety and can be made by crossing inbreds PH8JV andPH17C4. Locus conversions of Hybrid Maize Variety X18A643 can be made bycrossing inbreds PH8JV and PH17C4 wherein PH8JV and/or PH17C4 comprise alocus conversion(s). Hybrid Maize Variety X18A643 has a relativematurity of approximately 115 based on the Comparative Relative MaturityRating System for harvest moisture of grain. The yield platform BLUPvalue for Hybrid Maize Variety X18A643 is 209.5 bushels per acre. Theyield platform BLUP is a value derived by averaging for all members ofthe platform weighted by the inverse of the Standard Errors.

The maize variety has shown uniformity and stability within the limitsof environmental influence for all the traits as described in theVariety Description Information (Table 1, found at the end of thesection). The inbred parents of this maize variety have beenself-pollinated and ear-rowed a sufficient number of generations withcareful attention paid to uniformity of plant type to ensure thehomozygosity and phenotypic stability necessary for use in commercialhybrid seed production. The variety has been increased both by hand andin isolated fields with continued observation for uniformity. No varianttraits have been observed or are expected in X18A643.

Hybrid Maize Variety X18A643 can be reproduced by planting seeds of theinbred parent varieties, growing the resulting maize plants under crosspollinating conditions, and harvesting the resulting seed usingtechniques familiar to the agricultural arts.

Genotypic Characteristics of X18A643

In addition to phenotypic observations, a plant can also be described byits genotype. The genotype of a plant can be characterized through agenetic marker profile. There are many laboratory-based techniquesavailable for the analysis, comparison and characterization of plantgenotype; among these are Isozyme Electrophoresis, Restriction FragmentLength Polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs(RAPDs), Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNAAmplification Fingerprinting (DAF), Sequence Characterized AmplifiedRegions (SCARs), Amplified Fragment Length Polymorphisms (AFLPs), SimpleSequence Repeats (SSRs) which are also referred to as Microsatellites,and Single Nucleotide Polymorphisms (SNPs). For example, see Berry, Don,et al., “Assessing Probability of Ancestry Using Simple Sequence RepeatProfiles Applications to Maize Hybrids and Inbreds”, Genetics, 2002,161: 813-824, and Berry, Don et al., “Assessing Probability of AncestryUsing Simple Sequence Repeat Profiles: Applications to Maize InbredLines and Soybean Varieties”, Genetics, 2003, 165: 331-342, which areincorporated by reference herein in their entirety.

Particular markers used for these purposes may include any type ofmarker and marker profile which provides a means of distinguishingvarieties. In addition to being used for identification of maize varietyX18A643 and its plant parts, the genetic marker profile is also usefulin developing a locus conversion of X18A643.

Means of performing genetic marker profiles using SSR polymorphisms arewell known in the art. SSRs are genetic markers based on polymorphismsin repeated nucleotide sequences, such as microsatellites. A markersystem based on SSRs can be highly informative in linkage analysisrelative to other marker systems in that multiple alleles may bepresent. Another advantage of this type of marker is that, through useof flanking primers, detection of SSRs can be achieved, for example, bythe polymerase chain reaction (PCR), thereby eliminating the need forlabor-intensive Southern hybridization. The PCR™ detection is done byuse of two oligonucleotide primers flanking the polymorphic segment ofrepetitive DNA. Repeated cycles of heat denaturation of the DNA followedby annealing of the primers to their complementary sequences at lowtemperatures, and extension of the annealed primers with DNA polymerase,comprise the major part of the methodology.

Following amplification, markers can be scored by gel electrophoresis ofthe amplification products. Scoring of marker genotype is based on thesize of the amplified fragment, which may be measured by the base pairweight or molecular weight of the fragment. While variation in theprimer used or in laboratory procedures can affect the reportedmolecular weight, relative values should remain constant regardless ofthe specific primer or laboratory used. When comparing plants it ispreferable if all SSR profiles are performed in the same lab. An SSRservice is available to the public on a contractual basis by DNALandmarks in Saint-Jean-sur-Richelieu, Quebec, Canada.

Primers used for SSRs are publicly available and may be found in theMaize GDB on the World Wide Web at maizegdb.org (sponsored by the USDAAgricultural Research Service), in Sharopova et al. (Plant Mol. Biol.48(5-6):463-481), Lee et al. (Plant Mol. Biol. 48(5-6); 453-461).Primers may be constructed from publicly available sequence information.Some marker information may be available from DNA Landmarks.

Comparisons of Pioneer Maize Variety Hybrid X18A643

In addition to knowledge of the germplasm and plant genetics, a part ofthe hybrid selection process is dependent on experimental design coupledwith the use of statistical analysis. Experimental design andstatistical analysis are used to help determine which hybridcombinations are significantly better or different for one or moretraits of interest. Experimental design methods are used to assess errorso that differences between two hybrid varieties can be more accuratelyevaluated. Statistical analysis includes the calculation of mean values,determination of the statistical significance of the sources ofvariation, and the calculation of the appropriate variance components.One of ordinary skill in the art of plant breeding would know how toevaluate the traits of two plant varieties to determine if there is nosignificant difference between the two traits expressed by thosevarieties. For example, see Fehr, Walt, Principles of CultivarDevelopment, pages 261-286 (1987). Mean trait values may be used todetermine whether trait differences are significant. Trait values shouldpreferably be measured on plants grown under the same environmentalconditions, and environmental conditions should be appropriate for thetraits or traits being evaluated. Sufficient selection pressure shouldbe present for optimum measurement of traits of interest such asherbicide, insect or disease resistance. For example, a locus conversionof X18A643 for herbicide resistance should be compared with an isogeniccounterpart in the absence of the herbicide.

In Table 2, found at the end of this section, BLUP, Best Linear UnbiasedPrediction, values are reported for maize hybrid X18A643 and/or maizehybrid X18A643 comprising locus conversions. BLUP values are alsoreported for other hybrids adapted to the same growing region as maizehybrid X18A643 with corresponding locus conversions. The BLUP values andStandard Errors, SE, are reported for numerous traits. In Table 2 therows indicating the values for the maize hybrid X18A643 and/or maizehybrid X18A643 comprising locus conversions are immediately followed bya hybrid or hybrids adapted to the same growing region and comprisingthe corresponding traits.

Development of Maize Hybrids Using X18A643

During the inbreeding process in maize, the vigor of the varietiesdecreases. However, vigor is restored when two different inbredvarieties are crossed to produce the hybrid progeny (F1). An importantconsequence of the homozygosity and homogeneity of the inbred varietiesis that the hybrid between a defined pair of inbreds may be reproducedindefinitely as long as the homogeneity of the inbred parents ismaintained. Once the inbreds that create a superior hybrid have beenidentified, a continual supply of the hybrid seed can be produced usingthese inbred parents and the hybrid corn plants can then be generatedfrom this hybrid seed supply.

X18A643 may also be used to produce a double cross hybrid or a three-wayhybrid. A single cross hybrid is produced when two inbred varieties arecrossed to produce the F1 progeny. A double cross hybrid is producedfrom four inbred varieties crossed in pairs (A×B and C×D) and then thetwo F1 hybrids are crossed again (A×B)×(C×D). A three-way cross hybridis produced from three inbred varieties where two of the inbredvarieties are crossed (A×B) and then the resulting F1 hybrid is crossedwith the third inbred variety (A×B)×C. In each case, pericarp tissuefrom the female parent will be a part of and protect the hybrid seed.Another form of commercial hybrid production involves the use of amixture of male sterile hybrid seed and male pollinator seed. Whenplanted, the resulting male sterile hybrid plants are pollinated by thepollinator plants. This method is primarily used to produce grain withenhanced quality grain traits, such as high oil, because desired qualitygrain traits expressed in the pollinator will also be expressed in thegrain produced on the male sterile hybrid plant. In this method thedesired quality grain trait does not have to be incorporated by lengthyprocedures such as recurrent backcross selection into an inbred parentline. One use of this method is described in U.S. Pat. Nos. 5,704,160and 5,706,603.

Locus Conversions of Hybrid Maize Variety X18A643

X18A643 represents a new base genetic line into which a new locus ortrait may be introduced. Direct transformation and backcrossingrepresent two important methods that can be used to accomplish such anintrogression. The term locus conversion is used to designate theproduct of such an introgression.

To select and develop a superior hybrid, it is necessary to identify andselect genetically unique individuals that occur in a segregatingpopulation. The segregating population is the result of a combination ofcrossover events plus the independent assortment of specificcombinations of alleles at many gene loci that results in specific andunique genotypes. Once such a variety is developed its value to societyis substantial since it is important to advance the germplasm base as awhole in order to maintain or improve traits such as yield, diseaseresistance, pest resistance and plant performance in extreme weatherconditions. Locus conversions are routinely used to add or modify one ora few traits of such a line and this further enhances its value andusefulness to society.

Backcrossing can be used to improve inbred varieties and a hybridvariety which is made using those inbreds. Backcrossing can be used totransfer a specific desirable trait from one variety, the donor parent,to an inbred called the recurrent parent which has overall goodagronomic characteristics yet that lacks the desirable trait. Thistransfer of the desirable trait into an inbred with overall goodagronomic characteristics can be accomplished by first crossing arecurrent parent to a donor parent (non-recurrent parent). The progenyof this cross is then mated back to the recurrent parent followed byselection in the resultant progeny for the desired trait to betransferred from the non-recurrent parent.

Traits may be used by those of ordinary skill in the art to characterizeprogeny. Traits are commonly evaluated at a significance level, such asa 1%, 5% or 10% significance level, when measured in plants grown in thesame environmental conditions. For example, a locus conversion ofX18A643 may be characterized as having essentially the same phenotypictraits as X18A643. The traits used for comparison may be those traitsshown in Table 1 or Table 2. Molecular markers can also be used duringthe breeding process for the selection of qualitative traits. Forexample, markers can be used to select plants that contain the allelesof interest during a backcrossing breeding program. The markers can alsobe used to select for the genome of the recurrent parent and against thegenome of the donor parent. Using this procedure can minimize the amountof genome from the donor parent that remains in the selected plants.

A locus conversion of X18A643 will retain the genetic integrity ofX18A643. A locus conversion of X18A643 will comprise at least 92%, 93%,94%, 95%, 96%, 97%, 98% or 99% of the base genetics of X18A643 asdetermined by using SSR markers or SNP markers. For example, a locusconversion of X18A643 can be developed when DNA sequences are introducedthrough backcrossing (Hallauer et al., 1988), with a parent of X18A643utilized as the recurrent parent. Both naturally occurring andtransgenic DNA sequences may be introduced through backcrossingtechniques. A backcross conversion may produce a plant with a locusconversion in at least one or more backcrosses, including at least 2crosses, at least 3 crosses, at least 4 crosses, at least 5 crosses andthe like. Molecular marker assisted breeding or selection may beutilized to reduce the number of backcrosses necessary to achieve thebackcross conversion. For example, see Openshaw, S. J. et al.,Marker-assisted Selection in Backcross Breeding. In: ProceedingsSymposium of the Analysis of Molecular Data, August 1994, Crop ScienceSociety of America, Corvallis, Oreg., where it is demonstrated that abackcross conversion can be made in as few as two backcrosses.

The complexity of the backcross conversion method depends on the type oftrait being transferred (single genes or closely linked genes as vs.unlinked genes), the level of expression of the trait, the type ofinheritance (cytoplasmic or nuclear) and the types of parents includedin the cross. It is understood by those of ordinary skill in the artthat for single locus traits that are relatively easy to classify, thebackcross method is effective and relatively easy to manage. (SeeHallauer et al. in Corn and Corn Improvement, Sprague and Dudley, ThirdEd. 1998). Desired traits that may be transferred through locusconversion include, but are not limited to, waxy starch, sterility(nuclear and cytoplasmic), fertility restoration, grain color (white),drought resistance enhanced nitrogen utilization efficiency, alterednitrogen responsiveness, altered fatty acid profile, disease resistance(bacterial, fungal or viral), insect resistance, herbicide tolerance andyield enhancements. In addition, an introgression site itself, such asan FRT site, Lox site or other site specific integration site, may beinserted by backcrossing and utilized for direct insertion of one ormore genes of interest into a specific plant variety. The trait ofinterest is transferred from the donor parent to the recurrent parent,in this case, an inbred parent of the maize variety disclosed herein.

The seed industry commonly markets “triple stacks” of base genetics;which can be varieties comprising a locus conversion of at least 3 loci.Similarly, “quadruple stacks” would comprise the base genetics and couldcomprise a locus conversion of at least 4 loci. Stacking of traits iscommon to those of ordinary skill in the art of plant breeding andstacked traits account for a significant percentage of commercial cornhybrid sales. For example, figures from Purdue University show thatbiotech-trait corn accounted for 61% of all corn acres in 2006 and cornwith two or more stacked traits accounted for 11.9 million acres. That'sa significant portion of the approximately 80 million acres of corngrown in the United States. In addition, for 2007 at least one companyprojects selling more triple-stack corn hybrids than single traithybrids. (Wayne Wenzel, “Double, Triple, Quad”, published Nov. 8, 2006,Agweb.com, accessed Dec. 4, 2006). A single locus may contain severaltransgenes, such as a transgene for disease resistance that, in the sameexpression vector, also contains a transgene for herbicide tolerance. Asused herein, the phrase ‘comprising a’ transgene, transgenic event orlocus conversion means one or more transgenes, transgenic events orlocus conversions. The gene for herbicide tolerance may be used as aselectable marker and/or as a phenotypic trait. A locus trait conversionof a site specific integration system allows for the integration ofmultiple genes at the converted loci. Further, SSI and FRT technologiesknown to those of skill in the art may result in multiple geneintrogressions at a single locus.

The locus conversion may result from either the transfer of a dominantallele or a recessive allele. Selection of progeny containing the traitof interest is accomplished by direct selection for a trait associatedwith a dominant allele. Transgenes transferred via backcrossingtypically function as a dominant single gene trait and are relativelyeasy to classify. Selection of progeny for a trait that is transferredvia a recessive allele, such as the waxy starch characteristic, requiresgrowing and selfing the first backcross generation to determine whichplants carry the recessive alleles. Recessive traits may requireadditional progeny testing in successive backcross generations todetermine the presence of the locus of interest. The last backcrossgeneration is usually selfed to give pure breeding progeny for thegene(s) being transferred, although a backcross conversion with a stablyintrogressed trait may also be maintained by further backcrossing to therecurrent parent with selection for the converted trait.

Along with selection for the trait of interest, progeny are selected forthe phenotype and/or genotype of the recurrent parent. Whileoccasionally additional polynucleotide sequences or genes may betransferred along with the backcross conversion, the backcrossconversion variety “fits into the same hybrid combination as therecurrent parent inbred variety and contributes the effect of theadditional gene added through the backcross.” See Poehlman et al. (1995,page 334). It has been proposed that in general there should be at leastfour backcrosses when it is important that the recovered varieties beessentially identical to the recurrent parent except for thecharacteristic being transferred (Fehr 1987, Principles of CultivarDevelopment). However, as noted above, the number of backcrossesnecessary can be reduced with the use of molecular markers. Otherfactors, such as a genetically similar donor parent, may also reduce thenumber of backcrosses necessary. When one or more traits areintrogressed into the variety a difference in quantitative agronomictraits, such as yield or dry down, between the variety and anintrogressed version of the variety may occur. For example, the varietywith a locus conversion, may provide a net yield increase inenvironments where the trait provides a benefit, such as when a varietywith an introgressed trait for insect resistance is grown in anenvironment where insect pressure exists, or when a variety withherbicide tolerance is grown in an environment where the herbicide ispresent. There also may be instances where a locus conversion will causea decrease in yield.

Male Sterility and Hybrid Seed Production

Hybrid seed production requires elimination or inactivation of pollenproduced by the female inbred parent. Incomplete removal or inactivationof the pollen provides the potential for self-pollination. A reliablemethod of controlling male fertility in plants offers the opportunityfor improved seed production. There are several ways in which a maizeplant can be manipulated so that it is male sterile. These include useof manual or mechanical emasculation (or detasseling), use of one ormore genetic factors that confer male sterility, including cytoplasmicgenetic and/or nuclear genetic male sterility, use of gametocides andthe like. All of such embodiments are within the scope of the presentclaims. The term manipulated to be male sterile refers to the use of anyavailable techniques to produce a male sterile version of maize varietyX18A643. The male sterility may be either partial or complete malesterility.

Hybrid maize seed is often produced by a male sterility systemincorporating manual or mechanical detasseling. Alternate strips of twoinbred varieties of maize are planted in a field, and the pollen-bearingtassels are removed from one of the inbreds (female) prior to pollenshed. Providing that there is sufficient isolation from sources offoreign maize pollen, the ears of the detasseled inbred will befertilized only from the other inbred (male), and the resulting seed istherefore hybrid and will form hybrid plants.

Large scale commercial maize hybrid production, as it is practicedtoday, requires the use of some form of male sterility system whichcontrols or inactivates male fertility. A reliable method of controllingmale fertility in plants also offers the opportunity for improved plantbreeding. This is especially true for development of maize hybrids,which relies upon some sort of male sterility system. There are severalways in which a maize plant can be manipulated so that is male sterile.These include use of manual or mechanical emasculation (or detasseling),cytoplasmic genetic male sterility, nuclear genetic male sterility,gametocides and the like.

The laborious detasseling process can be avoided by using cytoplasmicmale-sterile (CMS) inbreds. Plants of a CMS inbred are male sterile as aresult of genetic factors in the cytoplasm, as opposed to the nucleus,and so nuclear linked genes are not transferred during backcrossing.Thus, this characteristic is inherited exclusively through the femaleparent in maize plants, since only the female provides cytoplasm to thefertilized seed. CMS plants are fertilized with pollen from anotherinbred that is not male-sterile. Pollen from the second inbred may ormay not contribute genes that make the hybrid plants male-fertile, andeither option may be preferred depending on the intended use of thehybrid. The same hybrid seed, a portion produced from detasseled fertilemaize and a portion produced using the CMS system can be blended toinsure that adequate pollen loads are available for fertilization whenthe hybrid plants are grown. CMS systems have been successfully usedsince the 1950's, and the male sterility trait is routinely backcrossedinto inbred varieties. See Wych, p. 585-586, 1998.

There are several methods of conferring genetic male sterilityavailable, such as multiple mutant genes at separate locations withinthe genome that confer male sterility, as disclosed in U.S. Pat. Nos.4,654,465 and 4,727,219 to Brar et al. and chromosomal translocations asdescribed by Patterson in U.S. Pat. Nos. 3,861,709 and 3,710,511. Theseand all patents referred to are incorporated by reference. In additionto these methods, Albertsen et al., of Pioneer Hi-Bred, U.S. Pat. No.5,432,068, describe a system of nuclear male sterility which includes:identifying a gene which is critical to male fertility; silencing thisnative gene which is critical to male fertility; removing the nativepromoter from the essential male fertility gene and replacing it with aninducible promoter; inserting this genetically engineered gene back intothe plant; and thus creating a plant that is male sterile because theinducible promoter is not “on” resulting in the male fertility gene notbeing transcribed. Fertility is restored by inducing, or turning “on”,the promoter, which in turn allows the gene that confers male fertilityto be transcribed.

These and the other methods of conferring genetic male sterility in theart, each possess their own benefits and drawbacks. Some other methodsuse a variety of approaches such as delivering into the plant a geneencoding a cytotoxic substance associated with a male tissue specificpromoter or an antisense system in which a gene critical to fertility isidentified and an antisense to that gene is inserted in the plant (seeFabinjanski, et al. EPO 89/3010153.8 Publication No. 329,308 and PCTApplication PCT/CA90/00037 published as WO 90/08828).

Another system useful in controlling male sterility makes use ofgametocides. Gametocides are not a genetic system, but rather a topicalapplication of chemicals. These chemicals affect cells that are criticalto male fertility. The application of these chemicals affects fertilityin the plants only for the growing season in which the gametocide isapplied (see Carlson, Glenn R., U.S. Pat. No. 4,936,904).

Application of the gametocide, timing of the application and genotypespecificity often limit the usefulness of the approach and it is notappropriate in all situations.

Transformation

The advent of new molecular biological techniques has allowed theisolation and characterization of genetic elements with specificfunctions, such as encoding specific protein products. Scientists in thefield of plant biology developed a strong interest in engineering thegenome of plants to contain and express foreign genetic elements, oradditional, or modified versions of native or endogenous geneticelements in order to alter the traits of a plant in a specific manner.Any DNA sequences, whether from a different species or from the samespecies, which are stably inserted into the cell using transformationare referred to herein collectively as “transgenes” and/or “transgenicevents”. In some embodiments of the invention, a transformed variant ofX18A643 may comprise at least one transgene but could contain at least1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and/or no more than 15, 14, 13, 12, 11,10, 9, 8, 7, 6, 5, 4, 3, or 2. Over the last fifteen to twenty yearsseveral methods for producing transgenic plants have been developed, andthe present invention also relates to transformed versions of theclaimed maize variety X18A643 as well as combinations thereof.

Numerous methods for plant transformation have been developed, includingbiological and physical plant transformation protocols. See, forexample, Miki et al., “Procedures for Introducing Foreign DNA intoPlants” in Methods in Plant Molecular Biology and Biotechnology, Glick,B. R. and Thompson, J. E. Eds. (CRC Press, Inc., Boca Raton, 1993) pages67-88 and Armstrong, “The First Decade of Maize Transformation: A Reviewand Future Perspective” (Maydica 44:101-109, 1999). In addition,expression vectors and in vitro culture methods for plant cell or tissuetransformation and regeneration of plants are available. See, forexample, Gruber et al., “Vectors for Plant Transformation” in Methods inPlant Molecular Biology and Biotechnology, Glick, B. R. and Thompson, J.E. Eds. (CRC Press, Inc., Boca Raton, 1993) pages 89-119.

The most prevalent types of plant transformation involve theconstruction of an expression vector. Such a vector comprises a DNAsequence that contains a gene under the control of or operatively linkedto a regulatory element, for example a promoter. The vector may containone or more genes and one or more regulatory elements.

A transgenic event which has been stably engineered into the germ cellline of a particular maize plant using transformation techniques, couldbe moved into the germ cell line of another variety using traditionalbreeding techniques that are well known in the plant breeding arts.These varieties can then be crossed to generate a hybrid maize varietyplant such as maize variety plant X18A643 which comprises a transgenicevent. For example, a backcrossing approach is commonly used to move atransgenic event from a transformed maize plant to another variety, andthe resulting progeny would then comprise the transgenic event(s). Also,if an inbred variety was used for the transformation then the transgenicplants could be crossed to a different inbred in order to produce atransgenic hybrid maize plant.

Various genetic elements can be introduced into the plant genome usingtransformation. These elements include, but are not limited to genes;coding sequences; inducible, constitutive, and tissue specificpromoters; enhancing sequences; and signal and targeting sequences. Forexample, see the traits, genes and transformation methods listed in U.S.Pat. Nos. 6,118,055 and 6,284,953, which are herein incorporated byreference. In addition, transformability of a variety can be increasedby introgressing the trait of high transformability from another varietyknown to have high transformability, such as Hi-II. See U.S. PatentApplication Publication No. 2004/0016030.

With transgenic plants according to the present invention, a foreignprotein can be produced in commercial quantities. Thus, techniques forthe selection and propagation of transformed plants, which are wellunderstood in the art, yield a plurality of transgenic plants that areharvested in a conventional manner, and a foreign protein then can beextracted from a tissue of interest or from total biomass. Proteinextraction from plant biomass can be accomplished by known methods whichare discussed, for example, by Heney and Orr, Anal. Biochem. 114: 92-6(1981).

Transgenic events can be mapped by one of ordinary skill in the art andsuch techniques are well known to those of ordinary skill in the art.For exemplary methodologies in this regard, see for example, Glick andThompson, Methods In Plant Molecular Biology And Biotechnology, 269-284(CRC Press, Boca Raton, 1993).

Likewise, by means of the present invention, plants can be geneticallyengineered to express various phenotypes of agronomic interest. Throughthe transformation of maize the expression of genes can be altered toenhance disease resistance, insect resistance, herbicide tolerance,agronomic traits, grain quality and other traits. Transformation canalso be used to insert DNA sequences which control or help controlmale-sterility. DNA sequences native to maize as well as non-native DNAsequences can be transformed into maize and used to alter levels ofnative or non-native proteins. Various promoters, targeting sequences,enhancing sequences, and other DNA sequences can be inserted into themaize genome for the purpose of altering the expression of proteins.Reduction of the activity of specific genes (also known as genesilencing, or gene suppression) is desirable for several aspects ofgenetic engineering in plants.

Many techniques for gene silencing are well known to one of skill in theart, including but not limited to knock-outs (such as by insertion of atransposable element such as mu (Vicki Chandler, The Maize Handbook ch.118 (Springer-Verlag 1994) or other genetic elements such as a FRT, Loxor other site specific integration site, antisense technology (see,e.g., Sheehy et al. (1988) PNAS USA 85:8805-8809; and U.S. Pat. Nos.5,107,065; 5,453,566; and 5,759,829); co-suppression (e.g., Taylor(1997) Plant Ce119:1245; Jorgensen (1990) Trends Biotech. 8(12):340-344;Flavell (1994) PNAS USA 91:3490-3496; Finnegan et al. (1994)Bio/Technology 12: 883-888; and Neuhuber et al. (1994) Mol. Gen. Genet.244:230-241); RNA interference (Napoli et al. (1990) Plant Cell2:279-289; U.S. Pat. No. 5,034,323; Sharp (1999) Genes Dev. 13:139-141;Zamore et al. (2000) Cell 101:25-33; and Montgomery et al. (1998) PNASUSA 95:15502-15507), virus-induced gene silencing (Burton, et al. (2000)Plant Cell 12:691-705; and Baulcombe (1999) Curr. Op. Plant Bio.2:109-113); target-RNA-specific ribozymes (Haseloff et al. (1988) Nature334: 585-591); hairpin structures (Smith et al. (2000) Nature407:319-320; WO 99/53050; and WO 98/53083); MicroRNA (Aukerman & Sakai(2003) Plant Cell 15:2730-2741); ribozymes (Steinecke et al. (1992) EMBOJ. 11:1525; and Perriman et al. (1993) Antisense Res. Dev. 3:253);oligonucleotide mediated targeted modification (e.g., WO 03/076574 andWO 99/25853); Zn-finger targeted molecules (e.g., WO 01/52620; WO03/048345; and WO 00/42219); and other methods or combinations of theabove methods known to those of skill in the art.

Exemplary nucleotide sequences that may be altered by geneticengineering include, but are not limited to, those categorized below.

1. Transgenes that Confer Resistance to Insects or Disease and thatEncode:

(A) Plant disease resistance genes. Plant defenses are often activatedby specific interaction between the product of a disease resistance gene(R) in the plant and the product of a corresponding avirulence (Avr)gene in the pathogen. A plant variety can be transformed with clonedresistance gene to engineer plants that are resistant to specificpathogen strains. See, for example Jones et al., Science 266: 789 (1994)(cloning of the tomato Cf-9 gene for resistance to Cladosporium fulvum);Martin et al., Science 262: 1432 (1993) (tomato Pto gene for resistanceto Pseudomonas syringae pv. tomato encodes a protein kinase); Mindrinoset al., Cell 78: 1089 (1994) (Arabidopsis RSP2 gene for resistance toPseudomonas syringae), McDowell & Woffenden, (2003) Trends Biotechnol.21(4): 178-83 and Toyoda et al., (2002) Transgenic Res. 11(6):567-82. Aplant resistant to a disease is one that is more resistant to a pathogenas compared to the wild type plant.

(B) A Bacillus thuringiensis protein, a derivative thereof or asynthetic polypeptide modeled thereon. See, for example, Geiser et al.,Gene 48: 109 (1986), who disclose the cloning and nucleotide sequence ofa Bt delta-endotoxin gene. Moreover, DNA molecules encodingdelta-endotoxin genes can be purchased from American Type CultureCollection (Rockville, Md.), for example, under ATCC Accession Nos.40098, 67136, 31995 and 31998. Other non-limiting examples of Bacillusthuringiensis transgenes being genetically engineered are given in thefollowing patents and patent applications and hereby are incorporated byreference for this purpose: 5,188,960; 5,689,052; 5,880,275; 5,986,177;7,105,332; 7,208,474; WO 91/14778; WO 99/31248; WO 01/12731; WO99/24581; WO 97/40162 and U.S. application Ser. Nos. 10/032,717;10/414,637; 11/018,615; 11/404,297; 11/404,638; 11/471,878; 11/780,501;11/780,511; 11/780,503; 11/953,648; 11/953,648; and 11/957,893.

(C) An insect-specific hormone or pheromone such as an ecdysteroid andjuvenile hormone, a variant thereof, a mimetic based thereon, or anantagonist or agonist thereof. See, for example, the disclosure byHammock et al., Nature 344: 458 (1990), of baculovirus expression ofcloned juvenile hormone esterase, an inactivator of juvenile hormone.

(D) An insect-specific peptide which, upon expression, disrupts thephysiology of the affected pest. For example, see the disclosures ofRegan, J. Biol. Chem. 269: 9 (1994) (expression cloning yields DNAcoding for insect diuretic hormone receptor); Pratt et al., Biochem.Biophys. Res. Comm. 163: 1243 (1989) (an allostatin is identified inDiploptera puntata); Chattopadhyay et al. (2004) Critical Reviews inMicrobiology 30 (1): 33-54 2004; Zjawiony (2004) J Nat Prod 67 (2):300-310; Carlini & Grossi-de-Sa (2002) Toxicon, 40 (11): 1515-1539;Ussuf et al. (2001) Curr Sci. 80 (7): 847-853; and Vasconcelos &Oliveira (2004) Toxicon 44 (4): 385-403. See also U.S. Pat. No.5,266,317 to Tomalski et al., who disclose genes encodinginsect-specific toxins.

(E) An enzyme responsible for a hyperaccumulation of a monterpene, asesquiterpene, a steroid, hydroxamic acid, a phenylpropanoid derivativeor another non-protein molecule with insecticidal activity.

(F) An enzyme involved in the modification, including thepost-translational modification, of a biologically active molecule; forexample, a glycolytic enzyme, a proteolytic enzyme, a lipolytic enzyme,a nuclease, a cyclase, a transaminase, an esterase, a hydrolase, aphosphatase, a kinase, a phosphorylase, a polymerase, an elastase, achitinase and a glucanase, whether natural or synthetic. See PCTapplication WO 93/02197 in the name of Scott et al., which discloses thenucleotide sequence of a callase gene. DNA molecules which containchitinase-encoding sequences can be obtained, for example, from the ATCCunder Accession Nos. 39637 and 67152. See also Kramer et al., InsectBiochem. Molec. Biol. 23: 691 (1993), who teach the nucleotide sequenceof a cDNA encoding tobacco hookworm chitinase, and Kawalleck et al.,Plant Molec. Biol. 21: 673 (1993), who provide the nucleotide sequenceof the parsley ubi4-2 polyubiquitin gene, and U.S. Pat. Nos. 6,563,020;7,145,060 and 7,087,810.

(G) A molecule that stimulates signal transduction. For example, see thedisclosure by Botella et al., Plant Molec. Biol. 24: 757 (1994), ofnucleotide sequences for mung bean calmodulin cDNA clones, and Griess etal., Plant Physiol. 104: 1467 (1994), who provide the nucleotidesequence of a maize calmodulin cDNA clone.

(H) A hydrophobic moment peptide. See PCT application WO 95/16776 andU.S. Pat. No. 5,580,852 disclosure of peptide derivatives of Tachyplesinwhich inhibit fungal plant pathogens) and PCT application WO 95/18855and U.S. Pat. No. 5,607,914 (teaches synthetic antimicrobial peptidesthat confer disease resistance).

(I) A membrane permease, a channel former or a channel blocker. Forexample, see the disclosure by Jaynes et al., Plant Sci. 89: 43 (1993),of heterologous expression of a cecropin-beta lytic peptide analog torender transgenic tobacco plants resistant to Pseudomonas solanacearum.

(J) A viral-invasive protein or a complex toxin derived therefrom. Forexample, the accumulation of viral coat proteins in transformed plantcells imparts resistance to viral infection and/or disease developmenteffected by the virus from which the coat protein gene is derived, aswell as by related viruses. See Beachy et al., Ann. Rev. Phytopathol.28: 451 (1990). Coat protein-mediated resistance has been conferred upontransformed plants against alfalfa mosaic virus, cucumber mosaic virus,tobacco streak virus, potato virus X, potato virus Y, tobacco etchvirus, tobacco rattle virus and tobacco mosaic virus. Id.

(K) An insect-specific antibody or an immunotoxin derived therefrom.Thus, an antibody targeted to a critical metabolic function in theinsect gut would inactivate an affected enzyme, killing the insect. Cf.Taylor et al., Abstract #497, SEVENTH INT'L SYMPOSIUM ON MOLECULARPLANT-MICROBE INTERACTIONS (Edinburgh, Scotland, 1994) (enzymaticinactivation in transgenic tobacco via production of single-chainantibody fragments).

(L) A virus-specific antibody. See, for example, Tavladoraki et al.,Nature 366: 469 (1993), who show that transgenic plants expressingrecombinant antibody genes are protected from virus attack.

(M) A developmental-arrestive protein produced in nature by a pathogenor a parasite. Thus, fungal endo alpha-1,4-D-polygalacturonasesfacilitate fungal colonization and plant nutrient release bysolubilizing plant cell wall homo-alpha-1,4-D-galacturonase. See Lamb etal., Bio/Technology 10: 1436 (1992). The cloning and characterization ofa gene which encodes a bean endopolygalacturonase-inhibiting protein isdescribed by Toubart et al., Plant J. 2: 367 (1992).

(N) A developmental-arrestive protein produced in nature by a plant. Forexample, Logemann et al., Bio/Technology 10: 305 (1992), have shown thattransgenic plants expressing the barley ribosome-inactivating gene havean increased resistance to fungal disease.

(O) Genes involved in the Systemic Acquired Resistance (SAR) Responseand/or the pathogenesis related genes. Briggs, S., Current Biology, 5(2)(1995), Pieterse & Van Loon (2004) Curr. Opin. Plant Bio. 7(4):456-64and Somssich (2003) Cell 113(7):815-6.

(P) Antifungal genes (Cornelissen and Melchers, Pl. Physiol.101:709-712, (1993) and Parijs et al., Planta 183:258-264, (1991) andBushnell et al., Can. J. of Plant Path. 20(2):137-149 (1998). Also seeU.S. application Ser. Nos. 09/950,933; 11/619,645; 11/657,710;11/748,994; 11/774,121 and U.S. Pat. Nos. 6,891,085 and 7,306,946.

(Q) Detoxification genes, such as for fumonisin, beauvericin,moniliformin and zearalenone and their structurally related derivatives.For example, see U.S. Pat. Nos. 5,716,820; 5,792,931; 5,798,255;5,846,812; 6,083,736; 6,538,177; 6,388,171 and 6,812,380.

(R) Cystatin and cysteine proteinase inhibitors. See U.S. Pat. No.7,205,453.

(S) Defensin genes. See WO03000863 and U.S. Pat. Nos. 6,911,577;6,855,865; 6,777,592 and 7,238,781.

(T) Genes conferring resistance to nematodes. See e.g. PCT ApplicationWO96/30517; PCT Application WO93/19181, WO 03/033651 and Urwin et al.,Planta 204:472-479 (1998), Williamson (1999) Curr Opin Plant Bio.2(4):327-31; and U.S. Pat. Nos. 6,284,948 and 7,301,069.

(U) Genes that confer resistance to Phytophthora Root Rot, such as theRps 1, Rps 1-a, Rps 1-b, Rps 1-c, Rps 1-d, Rps 1-e, Rps 1-k, Rps 2, Rps3-a, Rps 3-b, Rps 3-c, Rps 4, Rps 5, Rps 6, Rps 7 and other Rps genes.See, for example, Shoemaker et al, Phytophthora Root Rot Resistance GeneMapping in Soybean, Plant Genome IV Conference, San Diego, Calif.(1995).

(V) Genes that confer resistance to Brown Stem Rot, such as described inU.S. Pat. No. 5,689,035 and incorporated by reference for this purpose.

(W) Genes that confer resistance to Colletotrichum, such as described inUS Patent publication US20090035765 and incorporated by reference forthis purpose. This includes the Rcg locus that may be utilized as asingle locus conversion.

2. Transgenes that Confer Tolerance to a Herbicide, for Example:

(A) A herbicide that inhibits the growing point or meristem, such as animidazolinone or a sulfonylurea. Exemplary genes in this category codefor mutant ALS and AHAS enzyme as described, for example, by Lee et al.,EMBO J. 7: 1241 (1988), and Miki et al., Theor. Appl. Genet. 80: 449(1990), respectively. See also, U.S. Pat. Nos. 5,605,011; 5,013,659;5,141,870; 5,767,361; 5,731,180; 5,304,732; 4,761,373; 5,331,107;5,928,937; and 5,378,824; U.S. application Ser. No. 11/683,737, andinternational publication WO 96/33270.

(B) Glyphosate (resistance imparted by mutant5-enolpyruvl-3-phosphikimate synthase (EPSP) and aroA genes,respectively) and other phosphono compounds such as glufosinate(phosphinothricin acetyl transferase (PAT) and Streptomyceshygroscopicus phosphinothricin acetyl transferase (bar) genes), andpyridinoxy or phenoxy proprionic acids and cyclohexones (ACCaseinhibitor-encoding genes). See, for example, U.S. Pat. No. 4,940,835 toShah et al., which discloses the nucleotide sequence of a form of EPSPSwhich can confer glyphosate tolerance. U.S. Pat. No. 5,627,061 to Barryet al. also describes genes encoding EPSPS enzymes. See also U.S. Pat.Nos. 6,566,587; 6,338,961; 6,248,876 B1; 6,040,497; 5,804,425;5,633,435; 5,145,783; 4,971,908; 5,312,910; 5,188,642; 4,940,835;5,866,775; 6,225,114 B1; 6,130,366; 5,310,667; 4,535,060; 4,769,061;5,633,448; 5,510,471; Re. 36,449; RE 37,287 E; and 5,491,288; andinternational publications EP1173580; WO 01/66704; EP1173581 andEP1173582, which are incorporated herein by reference for this purpose.Glyphosate tolerance is also imparted to plants that express a gene thatencodes a glyphosate oxido-reductase enzyme as described more fully inU.S. Pat. Nos. 5,776,760 and 5,463,175, which are incorporated herein byreference for this purpose. In addition glyphosate tolerance can beimparted to plants by the over expression of genes encoding glyphosateN-acetyltransferase. See, for example, U.S. application Ser. Nos.10/427,692; 10/835,615 and 11/507,751. A DNA molecule encoding a mutantaroA gene can be obtained under ATCC accession No. 39256, and thenucleotide sequence of the mutant gene is disclosed in U.S. Pat. No.4,769,061 to Comai. European Patent Application No. 0 333 033 to Kumadaet al. and U.S. Pat. No. 4,975,374 to Goodman et al. disclose nucleotidesequences of glutamine synthetase genes which confer tolerance toherbicides such as L-phosphinothricin. The nucleotide sequence of aphosphinothricin-acetyl-transferase gene is provided in European PatentNo. 0 242 246 and 0 242 236 to Leemans et al. De Greef et al.,Bio/Technology 7: 61 (1989), describe the production of transgenicplants that express chimeric bar genes coding for phosphinothricinacetyl transferase activity. See also, U.S. Pat. Nos. 5,969,213;5,489,520; 5,550,318; 5,874,265; 5,919,675; 5,561,236; 5,648,477;5,646,024; 6,177,616 B1; and 5,879,903, which are incorporated herein byreference for this purpose. Exemplary genes conferring tolerance tophenoxy proprionic acids and cyclohexones, such as sethoxydim andhaloxyfop, are the Acc1-S1, Acc1-S2 and Acc1-S3 genes described byMarshall et al., Theor. Appl. Genet. 83: 435 (1992).

(C) A herbicide that inhibits photosynthesis, such as a triazine (psbAand gs+ genes) and a benzonitrile (nitrilase gene). Przibilla et al.,Plant Cell 3: 169 (1991), describe the transformation of Chlamydomonaswith plasmids encoding mutant psbA genes. Nucleotide sequences fornitrilase genes are disclosed in U.S. Pat. No. 4,810,648 to Stalker, andDNA molecules containing these genes are available under ATCC AccessionNos. 53435, 67441 and 67442. Cloning and expression of DNA coding for aglutathione S-transferase is described by Hayes et al., Biochem. J. 285:173 (1992).

(D) Acetohydroxy acid synthase, which has been found to make plants thatexpress this enzyme resistant to multiple types of herbicides, has beenintroduced into a variety of plants (see, e.g., Hattori et al. (1995)Mol Gen Genet 246:419). Other genes that confer tolerance to herbicidesinclude: a gene encoding a chimeric protein of rat cytochrome P4507A1and yeast NADPH-cytochrome P450 oxidoreductase (Shiota et al. (1994)Plant Physiol 106:17), genes for glutathione reductase and superoxidedismutase (Aono et al. (1995) Plant Cell Physiol 36:1687, and genes forvarious phosphotransferases (Datta et al. (1992) Plant Mol Biol 20:619).

(E) Protoporphyrinogen oxidase (protox) is necessary for the productionof chlorophyll, which is necessary for all plant survival. The protoxenzyme serves as the target for a variety of herbicidal compounds. Theseherbicides also inhibit growth of all the different species of plantspresent, causing their total destruction. The development of plantscontaining altered protox activity which are tolerant to theseherbicides are described in U.S. Pat. Nos. 6,288,306 B1; 6,282,837 B1;and 5,767,373; and international publication WO 01/12825.

3. Transgenes that Confer or Contribute to an Altered GrainCharacteristic, Such as:

(A) Altered fatty acids, for example, by

-   -   (1) Down-regulation of stearoyl-ACP desaturase to increase        stearic acid content of the plant. See Knultzon et al., Proc.        Natl. Acad. Sci. USA 89: 2624 (1992) and WO99/64579 (Genes for        Desaturases to Alter Lipid Profiles in Corn),    -   (2) Elevating oleic acid via FAD-2 gene modification and/or        decreasing linolenic acid via FAD-3 gene modification (see U.S.        Pat. Nos. 6,063,947; 6,323,392; 6,372,965 and WO 93/11245),    -   (3) Altering conjugated linolenic or linoleic acid content, such        as in WO 01/12800,    -   (4) Altering LEC1, AGP, Dek1, Superal1, mi1ps, various Ipa genes        such as Ipa1, Ipa3, hpt or hggt. For example, see WO 02/42424,        WO 98/22604, WO 03/011015, WO02/057439, WO03/011015, U.S. Pat.        Nos. 6,423,886, 6,197,561, 6,825,397, and U.S. Application        Serial Nos. US2003/0079247, US2003/0204870, and        Rivera-Madrid, R. et al. Proc. Natl. Acad. Sci. 92:5620-5624        (1995).

B) Altered phosphorus content, for example, by the

-   -   (1) Introduction of a phytase-encoding gene would enhance        breakdown of phytate, adding more free phosphate to the        transformed plant. For example, see Van Hartingsveldt et al.,        Gene 127: 87 (1993), for a disclosure of the nucleotide sequence        of an Aspergillus niger phytase gene.    -   (2) Modulating a gene that reduces phytate content. In maize,        this, for example, could be accomplished, by cloning and then        re-introducing DNA associated with one or more of the alleles,        such as the LPA alleles, identified in maize mutants        characterized by low levels of phytic acid, such as in WO        05/113778 and/or by altering inositol kinase activity as in WO        02/059324, US2003/0009011, WO 03/027243, US2003/0079247, WO        99/05298, U.S. Pat. No. 6,197,561, U.S. Pat. No. 6,291,224, U.S.        Pat. No. 6,391,348, WO2002/059324, US2003/0079247, Wo98/45448,        WO99/55882, WO01/04147.

(C) Altered carbohydrates effected, for example, by altering a gene foran enzyme that affects the branching pattern of starch or, a genealtering thioredoxin such as NTR and/or TRX (see. (See U.S. Pat. No.6,531,648 which is incorporated by reference for this purpose) and/or agamma zein knock out or mutant such as cs27 or TUSC27 or en27 (See U.S.Pat. No. 6,858,778 and US2005/0160488, US2005/0204418; which areincorporated by reference for this purpose). See Shiroza et al., J.Bacteriol. 170: 810 (1988) (nucleotide sequence of Streptococcus mutansfructosyltransferase gene), Steinmetz et al., Mol. Gen. Genet. 200: 220(1985) (nucleotide sequence of Bacillus subtilis levansucrase gene), Penet al., Bio/Technology 10: 292 (1992) (production of transgenic plantsthat express Bacillus lichenifonnis alpha-amylase), Elliot et al., PlantMolec. Biol. 21: 515 (1993) (nucleotide sequences of tomato invertasegenes), Søgaard et al., J. Biol. Chem. 268: 22480 (1993) (site-directedmutagenesis of barley alpha-amylase gene), and Fisher et al., PlantPhysiol. 102: 1045 (1993) (maize endosperm starch branching enzyme II),WO 99/10498 (improved digestibility and/or starch extraction throughmodification of UDP-D-xylose 4-epimerase, Fragile 1 and 2, Ref1, HCHL,C4H), U.S. Pat. No. 6,232,529 (method of producing high oil seed bymodification of starch levels (AGP)). The fatty acid modification genesmentioned herein may also be used to affect starch content and/orcomposition through the interrelationship of the starch and oilpathways.

(D) Altered antioxidant content or composition, such as alteration oftocopherol or tocotrienols. For example, see U.S. Pat. No. 6,787,683,US2004/0034886 and WO 00/68393 involving the manipulation of antioxidantlevels, and WO 03/082899 through alteration of a homogentisate geranylgeranyl transferase (hggt).

(E) Altered essential seed amino acids. For example, see U.S. Pat. No.6,127,600 (method of increasing accumulation of essential amino acids inseeds), U.S. Pat. No. 6,080,913 (binary methods of increasingaccumulation of essential amino acids in seeds), U.S. Pat. No. 5,990,389(high lysine), WO99/40209 (alteration of amino acid compositions inseeds), WO99/29882 (methods for altering amino acid content ofproteins), U.S. Pat. No. 5,850,016 (alteration of amino acidcompositions in seeds), WO98/20133 (proteins with enhanced levels ofessential amino acids), U.S. Pat. No. 5,885,802 (high methionine), U.S.Pat. No. 5,885,801 (high threonine), U.S. Pat. No. 6,664,445 (plantamino acid biosynthetic enzymes), U.S. Pat. No. 6,459,019 (increasedlysine and threonine), U.S. Pat. No. 6,441,274 (plant tryptophansynthase beta subunit), U.S. Pat. No. 6,346,403 (methionine metabolicenzymes), U.S. Pat. No. 5,939,599 (high sulfur), U.S. Pat. No. 5,912,414(increased methionine), WO98/56935 (plant amino acid biosyntheticenzymes), WO98/45458 (engineered seed protein having higher percentageof essential amino acids), WO98/42831 (increased lysine), U.S. Pat. No.5,633,436 (increasing sulfur amino acid content), U.S. Pat. No.5,559,223 (synthetic storage proteins with defined structure containingprogrammable levels of essential amino acids for improvement of thenutritional value of plants), WO96/01905 (increased threonine),WO95/15392 (increased lysine), US2003/0163838, US2003/0150014,US2004/0068767, U.S. Pat. No. 6,803,498, WO01/79516.

4. Genes that Control Male-Sterility:

There are several methods of conferring genetic male sterilityavailable, such as multiple mutant genes at separate locations withinthe genome that confer male sterility, as disclosed in U.S. Pat. Nos.4,654,465 and 4,727,219 to Brar et al. and chromosomal translocations asdescribed by Patterson in U.S. Pat. Nos. 3,861,709 and 3,710,511. Inaddition to these methods, Albertsen et al., U.S. Pat. No. 5,432,068,describe a system of nuclear male sterility which includes: identifyinga gene which is critical to male fertility; silencing this native genewhich is critical to male fertility; removing the native promoter fromthe essential male fertility gene and replacing it with an induciblepromoter; inserting this genetically engineered gene back into theplant; and thus creating a plant that is male sterile because theinducible promoter is not “on” resulting in the male fertility gene notbeing transcribed. Fertility is restored by inducing, or turning “on”,the promoter, which in turn allows the gene that confers male fertilityto be transcribed.

(A) Introduction of a deacetylase gene under the control of atapetum-specific promoter and with the application of the chemicalN-Ac-PPT (WO 01/29237).

(B) Introduction of various stamen-specific promoters (WO 92/13956, WO92/13957).

(C) Introduction of the barnase and the barstar gene (Paul et al. PlantMol. Biol. 19:611-622, 1992).

For additional examples of nuclear male and female sterility systems andgenes, see also, U.S. Pat. Nos. 5,859,341; 6,297,426; 5,478,369;5,824,524; 5,850,014; and 6,265,640; all of which are herebyincorporated by reference.

5. Genes that create a site for site specific DNA integration. Thisincludes the introduction of FRT sites that may be used in the FLP/FRTsystem and/or Lox sites that may be used in the Cre/Loxp system. Forexample, see Lyznik, et al., Site-Specific Recombination for GeneticEngineering in Plants, Plant Cell Rep (2003) 21:925-932 and WO 99/25821which are hereby incorporated by reference. Other systems that may beused include the Gin recombinase of phage Mu (Maeser et al., 1991; VickiChandler, The Maize Handbook ch. 118 (Springer-Verlag 1994), the Pinrecombinase of E. coli (Enomoto et al., 1983), and the R/RS system ofthe pSRi plasmid (Araki et al., 1992).6. Genes that affect abiotic stress resistance (including but notlimited to flowering, ear and seed development, enhancement of nitrogenutilization efficiency, altered nitrogen responsiveness, droughtresistance or tolerance, cold resistance or tolerance, and saltresistance or tolerance) and increased yield under stress. For example,see: WO 00/73475 where water use efficiency is altered throughalteration of malate; U.S. Pat. Nos. 5,892,009, 5,965,705, 5,929,305,5,891,859, 6,417,428, 6,664,446, 6,706,866, 6,717,034, 6,801,104,WO2000060089, WO2001026459, WO2001035725, WO2001034726, WO2001035727,WO2001036444, WO2001036597, WO2001036598, WO2002015675, WO2002017430,WO2002077185, WO2002079403, WO2003013227, WO2003013228, WO2003014327,WO2004031349, WO2004076638, WO9809521, and WO9938977 describing genes,including CBF genes and transcription factors effective in mitigatingthe negative effects of freezing, high salinity, and drought on plants,as well as conferring other positive effects on plant phenotype;US2004/0148654 and WO01/36596 where abscisic acid is altered in plantsresulting in improved plant phenotype such as increased yield and/orincreased tolerance to abiotic stress; WO2000/006341, WO04/090143, U.S.application Ser. Nos. 10/817,483 and 09/545,334 where cytokininexpression is modified resulting in plants with increased stresstolerance, such as drought tolerance, and/or increased yield. Also seeWO0202776, WO2003052063, JP2002281975, U.S. Pat. No. 6,084,153,WO0164898, U.S. Pat. No. 6,177,275, and U.S. Pat. No. 6,107,547(enhancement of nitrogen utilization and altered nitrogenresponsiveness). For ethylene alteration, see US20040128719,US20030166197 and WO200032761. For plant transcription factors ortranscriptional regulators of abiotic stress, see e.g. US20040098764 orUS20040078852.

Other genes and transcription factors that affect plant growth andagronomic traits such as yield, flowering, plant growth and/or plantstructure, can be introduced or introgressed into plants, see e.g.WO97/49811 (LHY), WO98/56918 (ESD4), WO97/10339 and U.S. Pat. No.6,573,430 (TFL), U.S. Pat. No. 6,713,663 (FT), WO96/14414 (CON),WO96/38560, WO01/21822 (VRN1), WO00/44918 (VRN2), WO99/49064 (GI),WO00/46358 (FR1), WO97/29123, U.S. Pat. No. 6,794,560, U.S. Pat. No.6,307,126 (GAI), WO99/09174 (D8 and Rht), and WO2004076638 andWO2004031349 (transcription factors).

Using X18A643 to Develop Another Maize Plant

The development of maize hybrids in a maize plant breeding programrequires, in general, the development of homozygous inbred lines, thecrossing of these lines, and the evaluation of the crosses. Maize plantbreeding programs combine the genetic backgrounds from two or moreinbred varieties or various other germplasm sources into breedingpopulations from which new inbred varieties are developed by selfing andselection of desired phenotypes. Hybrids also can be used as a source ofplant breeding material or as source populations from which to developor derive new maize varieties. Plant breeding techniques known in theart and used in a maize plant breeding program include, but are notlimited to, recurrent selection, mass selection, bulk selection,backcrossing, making double haploids, pedigree breeding, openpollination breeding, restriction fragment length polymorphism enhancedselection, genetic marker enhanced selection, and transformation. Oftencombinations of these techniques are used. The inbred varieties derivedfrom hybrids can be developed using plant breeding techniques asdescribed above. New inbreds are crossed with other inbred varieties andthe hybrids from these crosses are evaluated to determine which of thosehave commercial potential. The oldest and most traditional method ofanalysis is the observation of phenotypic traits but genotypic analysismay also be used. Descriptions of breeding methods can also be found inone of several reference books (e.g., Allard, Principles of PlantBreeding, 1960; Simmonds, Principles of Crop Improvement, 1979; Fehr,“Breeding Methods for Cultivar Development”, Production and Uses, 2^(nd)ed., Wilcox editor, 1987).

Recurrent Selection and Mass Selection

Recurrent selection is a method used in a plant breeding program toimprove a population of plants. X18A643 is suitable for use in arecurrent selection program. The method entails individual plants crosspollinating with each other to form progeny. The progeny are grown andthe superior progeny selected by any number of selection methods, whichinclude individual plant, half-sib progeny, full-sib progeny, selfedprogeny and toperossing. The selected progeny are cross pollinated witheach other to form progeny for another population. This population isplanted and again superior plants are selected to cross pollinate witheach other. Recurrent selection is a cyclical process and therefore canbe repeated as many times as desired. The objective of recurrentselection is to improve the traits of a population. The improvedpopulation can then be used as a source of breeding material to obtaininbred varieties to be used in hybrids or used as parents for asynthetic cultivar. A synthetic cultivar is the resultant progeny formedby the intercrossing of several selected inbreds.

X18A643 is suitable for use in mass selection. Mass selection is auseful technique when used in conjunction with molecular marker enhancedselection. In mass selection seeds from individuals are selected basedon phenotype and/or genotype. These selected seeds are then bulked andused to grow the next generation. Bulk selection requires growing apopulation of plants in a bulk plot, allowing the plants toself-pollinate, harvesting the seed in bulk and then using a sample ofthe seed harvested in bulk to plant the next generation. Instead of selfpollination, directed pollination could be used as part of the breedingprogram.

Production of Double Haploids

The production of double haploids from X18A643 can also be used for thedevelopment of inbreds. Double haploids are produced by the doubling ofa set of chromosomes (1 N) from a heterozygous plant to produce acompletely homozygous individual. For example, a further embodiment ofthis invention is the method of obtaining a substantially homozygousX18A643 progeny plant by obtaining a seed from the cross of X18A643 andanother maize plant and applying double haploid methods to the F1 seedor F1 plant or to any successive filial generation. Such methodssubstantially decrease the number of generations required to produce aninbred with similar genetics or characteristics to X18A643. For example,see Wan et al., “Efficient Production of Doubled Haploid Plants ThroughColchicine Treatment of Anther-Derived Maize Callus”, Theoretical andApplied Genetics, 77:889-892, 1989 and U.S. Patent Application2003/0005479. This can be advantageous because the process omits thegenerations of selfing needed to obtain a homozygous plant from aheterozygous source.

Haploid induction systems have been developed for various plants toproduce haploid tissues, plants and seeds. The haploid induction systemcan produce haploid plants from any genotype by crossing a selectedvariety (as female) with an inducer variety. Such inducer varieties formaize include Stock 6 (Coe, 1959, Am. Nat. 93:381-382; Sharkar and Coe,1966, Genetics 54:453-464) RWS (see the World Wide Web atuni-hohenheim.de/%7Eipspwww/350b/indexe.html#Project3), KEMS (Deimling,Roeber, and Geiger, 1997, Vortr. Pflanzenzuchtg 38:203-224), or KMS andZMS (Chalyk, Bylich & Chebotar, 1994, MNL 68:47; Chalyk & Chebotar,2000, Plant Breeding 119:363-364), and indeterminate gametophyte (ig)mutation (Kermicle 1969 Science 166:1422-1424), the disclosures of whichare incorporated herein by reference.

Methods for obtaining haploid plants are also disclosed in Kobayashi, M.et al., Journ. of Heredity 71(1):9-14, 1980, Pollacsek, M., Agronomie(Paris) 12(3):247-251, 1992; Cho-Un-Haing et al., Journ. of Plant Biol.,1996, 39(3):185-188; Verdoodt, L., et al., February 1998, 96(2):294-300;Genetic Manipulation in Plant Breeding, Proceedings InternationalSymposium Organized by EUCARPIA, Sep. 8-13, 1985, Berlin, Germany;Chalyk et al., 1994, Maize Genet Coop. Newsletter 68:47; Chalyk, S. T.,1999, Maize Genet. Coop. Newsletter 73:53-54; Coe, R. H., 1959, Am. Nat.93:381-382; Deimling, S. et al., 1997, Vortr. Pflanzenzuchtg 38:203-204;Kato, A., 1999, J. Hered. 90:276-280; Lashermes, P. et al., 1988, Theor.Appl. Genet. 76:570-572 and 76:405-410; Tyrnov, V. S. et al., 1984,Dokl. Akad. Nauk. SSSR 276:735-738; Zabirova, E. R. et al., 1996,Kukuruza I Sorgo N4, 17-19; Aman, M. A., 1978, Indian J. Genet PlantBreed 38:452-457; Chalyk S. T., 1994, Euphytica 79:13-18; Chase, S. S.,1952, Agron. J. 44:263-267; Coe, E. H., 1959, Am. Nat. 93:381-382; Coe,E. H., and Sarkar, K. R., 1964 J. Hered. 55:231-233; Greenblatt, I. M.and Bock, M., 1967, J. Hered. 58:9-13; Kato, A., 1990, Maize Genet.Coop. Newsletter 65:109-110; Kato, A., 1997, Sex. Plant Reprod.10:96-100; Nanda, D. K. and Chase, S. S., 1966, Crop Sci. 6:213-215;Sarkar, K. R. and Coe, E. H., 1966, Genetics 54:453-464; Sarkar, K. R.and Coe, E. H., 1971, Crop Sci. 11:543-544; Sarkar, K. R. and Sachan J.K. S., 1972, Indian J. Agric. Sci. 42:781-786; Kermicle J. L., 1969,Mehta Yeshwant, M. R., Genetics and Molecular Biology, September 2000,23(3):617-622; Tahir, M. S. et al. Pakistan Journal of Scientific andIndustrial Research, August 2000, 43(4):258-261; Knox, R. E. et al.Plant Breeding, August 2000, 119(4):289-298; U.S. Pat. No. 5,639,951 andU.S. patent application Ser. No. 10/121,200, the disclosures of whichare incorporated herein by reference.

Use of X18A643 in Tissue Culture

This invention is also directed to the use of maize variety X18A643 intissue culture. As used herein, the term “tissue culture” includes plantprotoplasts, plant cell tissue culture, cultured microspores, plantcalli, plant clumps, and the like. As used herein, phrases such as“growing the seed” or “grown from the seed” include embryo rescue,isolation of cells from seed for use in tissue culture, as well astraditional growing methods.

Duncan, Williams, Zehr, and Widholm, Planta, (1985) 165:322-332 reflectsthat 97% of the plants cultured which produced callus were capable ofplant regeneration. Subsequent experiments with both inbreds and hybridsproduced 91% regenerable callus which produced plants. In a furtherstudy in 1988, Songstad, Duncan & Widholm in Plant Cell Reports (1988),7:262-265 reports several media additions which enhance regenerabilityof callus of two inbred varieties. Other published reports alsoindicated that “nontraditional” tissues are capable of producing somaticembryogenesis and plant regeneration. K. P. Rao, et al., Maize GeneticsCooperation Newsletter, 60:64-65 (1986), refers to somatic embryogenesisfrom glume callus cultures and B. V. Conger, et al., Plant Cell Reports,6:345-347 (1987) indicates somatic embryogenesis from the tissuecultures of maize leaf segments. Thus, it is clear from the literaturethat the state of the art is such that these methods of obtaining plantsare, and were, “conventional” in the sense that they are routinely usedand have a very high rate of success.

Tissue culture of maize, including tassel/anther culture, is describedin U.S. Application 2002/0062506A1 and European Patent Application,Publication EPO160,390, each of which are incorporated herein byreference for this purpose. Maize tissue culture procedures are alsodescribed in Green and Rhodes, “Plant Regeneration in Tissue Culture ofMaize,” Maize for Biological Research (Plant Molecular BiologyAssociation, Charlottesville, Va. 1982, at 367-372) and in Duncan, etal., “The Production of Callus Capable of Plant Regeneration fromImmature Embryos of Numerous Zea Mays Genotypes,” 165 Planta 322-332(1985). Thus, another aspect of this invention is to provide cells whichupon growth and differentiation produce maize plants having the genotypeand/or phenotypic characteristics of maize variety X18A643.

INDUSTRIAL APPLICABILITY

Maize is used as human food, livestock feed, and as raw material inindustry. The food uses of maize, in addition to human consumption ofmaize kernels, include both products of dry- and wet-milling industries.The principal products of maize dry milling are grits, meal and flour.The maize wet-milling industry can provide maize starch, maize syrups,and dextrose for food use. Maize oil is recovered from maize germ, whichis a by-product of both dry- and wet-milling industries.

Maize, including both grain and non-grain portions of the plant, is alsoused extensively as livestock feed, primarily for beef cattle, dairycattle, hogs, and poultry.

Industrial uses of maize include production of ethanol, maize starch inthe wet-milling industry and maize flour in the dry-milling industry.The industrial applications of maize starch and flour are based onfunctional properties, such as viscosity, film formation, adhesiveproperties, and ability to suspend particles. The maize starch and flourhave application in the paper and textile industries. Other industrialuses include applications in adhesives, building materials, foundrybinders, laundry starches, explosives, oil-well muds, and other miningapplications.

Plant parts other than the grain of maize are also used in industry: forexample, stalks and husks are made into paper and wallboard and cobs areused for fuel and to make charcoal.

The seed of the maize variety, the plant produced from the seed, a plantproduced from crossing of maize variety X18A643 and various parts of themaize plant and transgenic versions of the foregoing, can be utilizedfor human food, livestock feed, and as a raw material in industry.

TABLE 1 VARIETY DESCRIPTION INFORMATION X18A643 AVG STDEV N 1. TYPE:(Describe intermediate types in comments section) 1 = Sweet, 2 = Dent, 3= Flint, 4 = Flour, 5 = Pop and 6 = Ornamental. 2 Comments: Dent-Flint2. MATURITY: DAYS HEAT UNITS Days H. Units Emergence to 50% of plants insilk 65 1,249 Emergence to 50% of plants in pollen shed 64 1,241 10% to90% pollen shed 5 74 3. PLANT Plant Height (to tassel tip) (cm) 320.213.08 10 Ear Height (to base of top ear node) (cm) 119.0 9.20 10 Lengthof Top Ear Internode (cm) 22.5 1.51 10 ** Average Number of Tillers perPlant 0.0 0.00 2 ** Average Number of Ears per Stalk 1.0 0.10 2Anthocyanin of Brace Roots: 1 = Absent, 2 = Faint, 2 3 = Moderate, 4 =Dark 4. LEAF: Width of Ear Node Leaf (cm) 9.6 0.84 10 Length of Ear NodeLeaf (cm) 96.8 5.12 10 Number of Leaves above Top Ear 6.5 0.53 10 LeafAngle: (at anthesis, 2nd leaf above ear to 20.5 5.50 10 stalk aboveleaf) (Degrees) * Leaf Color: V. Dark Green Munsell: 7.5GY34 Leaf SheathPubescence: 1 = none to 9 = like peach fuzz 3 5. TASSEL: Number ofPrimary Lateral Branches 9.0 1.89 10 Branch Angle from Central Spike(Degrees) 27.5 5.40 10 Tassel Length: (from peduncle node to tassel tip)(cm). 68.0 2.98 10 Pollen Shed: 0 = male sterile, 9 = heavy shed 7 *Anther Color: Buff Munsell: 2.5Y84 * Glume Color: Med. Green Munsell:2.5GY66 Bar Glumes (glume bands): 1= absent, 2 = present 1 PeduncleLength: (From top leaf node to lower branch) (cm) 30.1 2.85 10 6a. EAR(Unhusked ear) * Silk color: Red Munsell: 10RP38 (3 days after silkemergence) * Fresh husk color: Med. Green Munsell: 2.5GY66 * Dry huskcolor: White Munsell: 5Y8.52 (65 days after 50% silking) Ear position atdry husk stage: 3 1 = Upright, 2 = Horizontal, 3 = Pendant HuskTightness: (1 = very loose, 9 = very tight) 4 Husk Extension (atharvest): 1 = short (ears exposed), 2 2 = medium (<8 cm), 3 = long (8-10cm), 4 = v. long (>10 cm) 6b. EAR (Husked ear data) Ear Length (cm):19.8 1.48 10 Ear Diameter at mid-point (mm) 48.3 1.83 10 Ear Weight(gm): 243.0 38.84 10 Number of Kernel Rows: 15.0 1.05 10 Kernel Rows: 1= indistinct, 2 = distinct 2 Row Alignment: 1 = straight, 2 = slightlycurved, 3 = spiral 2 Shank Length (cm) 9.2 0.92 10 Ear Taper: 1 = slightcylind., 2 = average, 3 = extreme conic. 2 7. KERNEL (Dried): KernelLength (mm): 12.8 0.92 10 Kernel Width (mm): 8.5 0.53 10 KernelThickness (mm): 4.1 0.32 10 ** Round Kernels (shape grade) (%) 42.010.38 2 Aleurone Color Pattern: 1 = homozygous, 2 = segregating 1 *Aleurone Color: Yellow Munsell: 10YR814 * Hard Endo. Color: YellowMunsell: 10YR712 Endosperm Type: 3 1 = sweet (su1), 2 = extra sweet(sh2), 3 = normal starch, 4 = high amylose starch, 5 = waxy starch, 6 =high protein, 7 = high lysine, 8 = super sweet (se), 9 = high oil, 10 =other ** Weight per 100 Kernels (unsized sample) (gm): 30.5 2.12 2 8.COB: Cob Diameter at mid-point (mm): 25.1 0.99 10 Cob Color: RedMunsell: 10R38 * Munsell Glossy Book of Color, (A standard colorreference). Kollmorgen Inst. Corp. New Windsor, NY. ** Sample numberreflects the number of plots where the trait(s) was observed and not thenumber of individual plants scored

TABLE 2 BLUP values for hybrid X18A643 and other hybrids adapted to somegrowing region ANTROT BORBMN BRLPNE BRLPNL hybrid ft_note BLUP SE BLUPSE BLUP SE BLUP SE X18A643 (a,b) 56.1 4.8 97.2 3.7 33D49 4.1 0.4 85.72.4 53.9 4.0 87.6 3.5 33H27 4.8 0.4 78.9 2.7 26.8 3.5 57.1 3.5 BRTPCNBRTSTK CMSMT DIGENG hybrid ft_note BLUP SE BLUP SE BLUP SE BLUP SEX18A643 (a,b) 96.9 2.7 1810.6 5.4 33D49 96.6 1.3 98.5 1.2 91.0 2.91802.3 1.6 33H27 95.6 1.9 98.0 1.4 95.9 2.7 1810.0 2.0 EARHT ERTLPNEXTSTR GDUSHD hybrid ft_note BLUP SE BLUP SE BLUP SE BLUP SE X18A643(a,b) 56.2 0.6 67.2 0.3 137.1 0.8 33D49 50.4 0.2 82.0 2.0 67.9 0.1 138.00.3 33H27 48.4 0.3 79.0 2.2 67.9 0.1 135.1 0.4 GDUSLK GIBERS GLFSPTGOSWLT hybrid ft_note BLUP SE BLUP SE BLUP SE BLUP SE X18A643 (a,b)140.2 0.7 5.2 0.2 7.4 0.3 33D49 139.9 0.3 5.0 0.2 7.8 0.2 33H27 135.60.3 5.0 0.1 7.4 0.2 HDSMT HSKCVR HTFRM LRTLPN hybrid ft_note BLUP SEBLUP SE BLUP SE BLUP SE X18A643 (a,b) 62.1 4.5 5.9 0.2 38.3 0.1 84.4 4.033D49 90.4 2.5 5.3 0.1 38.5 0.0 85.3 2.1 33H27 89.2 2.5 6.5 0.2 38.6 0.075.1 2.2 MILKLN MST NLFBLT PLTHT hybrid ft_note BLUP SE BLUP SE BLUP SEBLUP SE X18A643 (a,b) 38.7 3.0 21.6 0.1 4.8 0.2 132.9 0.8 33D49 47.3 1.522.2 0.0 5.5 0.2 124.1 0.3 33H27 40.0 2.2 21.4 0.1 5.7 0.2 118.9 0.3STAGRN STKCTE STLLPN STLPCN hybrid ft_note BLUP SE BLUP SE BLUP SE BLUPSE X18A643 (a,b) 5.5 0.4 82.4 0.4 82.2 5.3 83.7 2.9 33D49 5.0 0.1 85.60.2 83.8 3.0 88.8 1.6 33H27 5.0 0.1 85.3 0.2 78.8 2.6 82.1 1.9 TSTWTNTSTWT hybrid ft_note BLUP SE BLUP SE X18A643 (a,b) 58.2 0.1 58.1 0.133D49 57.7 0.1 57.8 0.1 33H27 56.4 0.1 56.4 0.1 a wherein hybridcomprises a trait conversion conferring insect control b wherein hybridcomprises a trait conversion conferring herbicide tolerance c whereinhybrid comprises a trait conversion conferring disease control

DEPOSITS

Applicant(s) have made a deposit of at least 2500 seeds of parentalmaize inbred varieties PH8JV and PH17C4 with the American Type CultureCollection (ATCC), Manassas, Va. 20110 USA, ATCC Deposit Nos. PTA-7761and PTA-120279, respectively. The seeds deposited with the ATCC on Aug.9, 2006 for PTA-7761 and on Apr. 24, 2013 for PTA-120279, were obtainedfrom the seed of the variety maintained by Pioneer Hi-BredInternational, Inc., 7250 NW 62^(nd) Avenue, Johnston, Iowa 50131-1000since prior to the filing date of this application. Access to this seedwill be available during the pendency of the application to theCommissioner of Patents and Trademarks and persons determined by theCommissioner to be entitled thereto upon request. Upon allowance of anyclaims in the application, the Applicant(s) will make available to thepublic, pursuant to 37 C.F.R. §1.808, sample(s) of the deposit of atleast 2500 seeds of parental maize inbred varieties PH8JV and PH17C4with the American Type Culture Collection (ATCC), 10801 UniversityBoulevard, Manassas, Va. 20110-2209. This deposits of the seed ofparental maize inbred varieties for Hybrid Maize Variety X18A643 will bemaintained in the ATCC depository, which is a public depository, for aperiod of 30 years, or 5 years after the most recent request, or for theenforceable life of the patent, whichever is longer, and will bereplaced if it becomes nonviable during that period. Additionally,Applicant(s) have or will satisfy all the requirements of 37 C.F.R.§§1.801-1.809, including providing an indication of the viability of thesample upon deposit. Applicant(s) have no authority to waive anyrestrictions imposed by law on the transfer of biological material orits transportation in commerce. Applicant(s) do not waive anyinfringement of their rights granted under this patent or rightsapplicable to Hybrid Maize Variety X18A643 and/or its parental maizeinbred varieties PH8JV and PH17C4 under either the patent laws or thePlant Variety Protection Act (7 USC 2321 et seq.). Unauthorized seedmultiplication is prohibited.

REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated by reference.

-   Aukerman, M. J. et al. (2003) “Regulation of Flowering Time and    Floral Organ Identity by a MicroRNA and Its APETALA2-like Target    Genes” The Plant Cell 15:2730-2741-   Berry et al., “Assessing Probability of Ancestry Using Simple    Sequence Repeat Profiles: Applications to Maize Hybrids and    Inbreds”, Genetics 161:813-824 (2002)-   Berry et al., “Assessing Probability of Ancestry Using Simple    Sequence Repeat Profiles: Applications to Maize Inbred Lines and    Soybean Varieties” Genetics 165:331-342 (2003)-   Boppenmaier, et al., “Comparisons Among Strains of Inbreds for    RFLPs”, Maize Genetics Cooperative Newsletter, 65:1991, p. 90-   Conger, B. V., et al. (1987) “Somatic Embryogenesis From Cultured    Leaf Segments of Zea Mays”, Plant Cell Reports, 6:345-347-   Duncan, D. R., et al. (1985) “The Production of Callus Capable of    Plant Regeneration From Immature Embryos of Numerous Zea Mays    Genotypes”, Planta, 165:322-332

Edallo, et al. (1981) “Chromosomal Variation and Frequency ofSpontaneous Mutation Associated with in Vitro Culture and PlantRegeneration in Maize”, Maydica, XXVI: 39-56

-   Fehr, Walt, Principles of Cultivar Development, pages 261-286 (1987)-   Green, et al. (1975) “Plant Regeneration From Tissue Cultures of    Maize”, Crop Science, Vol. 15, pages 417-421-   Green, C. E., et al. (1982) “Plant Regeneration in Tissue Cultures    of Maize” Maize for Biological Research, pages 367-372-   Hallauer, A. R. et al. (1988) “Corn Breeding” Corn and Corn    Improvement, No. 18, pages 463-481-   Lee, Michael (1994) “Inbred Lines of Maize and Their Molecular    Markers”, The Maize Handbook, Ch. 65:423-432-   Meghji, M. R., et al. (1984) “Inbreeding Depression, Inbred & Hybrid    Grain Yields, and Other Traits of Maize Genotypes Representing Three    Eras”, Crop Science, Vol. 24, pages 545-549-   Openshaw, S. J., et al. (1994) “Marker-assisted selection in    backcross breeding”, pages 41-43. In Proceedings of the Symposium    Analysis of Molecular Marker Data. 5-7 Aug. 1994. Corvallis, Oreg.,    American Society for Horticultural Science/Crop Science Society of    America-   Phillips, et al. (1988) “Cell/Tissue Culture and In Vitro    Manipulation”, Corn & Corn Improvement, 3rd Ed., ASA Publication,    No. 18, pages 345-387-   Poehlman et al. (1995) Breeding Field Crop, 4th Ed., Iowa State    University Press, Ames, Iowa, pages 132-155 and 321-344-   Rao, K. V., et al., (1986) “Somatic Embryogenesis in Glume Callus    Cultures”, Maize Genetics Cooperative Newsletter, No. 60, pages    64-65-   Sass, John F. (1977) “Morphology”, Corn & Corn Improvement, ASA    Publication, Madison, Wis. pages 89-109-   Smith, J. S. C., et al., “The Identification of Female Selfs in    Hybrid Maize: A Comparison Using Electrophoresis and Morphology”,    Seed Science and Technology 14, 1-8-   Songstad, D. D. et al. (1988) “Effect of ACC    (1-aminocyclopropane-1-carboyclic acid), Silver Nitrate &    Norbonadiene on Plant Regeneration From Maize Callus Cultures”,    Plant Cell Reports, 7:262-265-   Tomes, et al. (1985) “The Effect of Parental Genotype on Initiation    of Embryogenic Callus From Elite Maize (Zea Mays L.) Germplasm”,    Theor. Appl. Genet., Vol. 70, p. 505-509

Troyer, et al. (1985) “Selection for Early Flowering in Corn: 10 LateSynthetics”, Crop Science, Vol. 25, pages 695-697

Umbeck, et al. (1983) “Reversion of Male-Sterile T-Cytoplasm Maize toMale Fertility in Tissue Culture”, Crop Science, Vol. 23, pages 584-588

-   Wan et al., “Efficient Production of Doubled Haploid Plants Through    Colchicine Treatment of Anther-Derived Maize Callus”, Theoretical    and Applied Genetics, 77:889-892, 1989-   Wright, Harold (1980) “Commercial Hybrid Seed Production”,    Hybridization of Crop Plants, Ch. 8:161-176-   Wych, Robert D. (1988) “Production of Hybrid Seed”, Corn and Corn    Improvement, Ch. 9, pages 565-607

The foregoing invention has been described in detail by way ofillustration and example for purposes of clarity and understanding. Asis readily apparent to one skilled in the art, the foregoing are onlysome of the methods and compositions that illustrate the embodiments ofthe foregoing invention. It will be apparent to those of ordinary skillin the art that variations, changes, modifications and alterations maybe applied to the compositions and/or methods described herein withoutdeparting from the true spirit, concept and scope of the invention.

What is claimed is:
 1. A seed of hybrid maize variety X18A643, producedby crossing a first plant of variety PH8JV with a second plant ofvariety PH17C4, wherein representative seed of said varieties PH8JV andPH17C4 have been deposited under ATCC Accession Number PTA-7761 andPTA-120279, respectively.
 2. A plant or plant part produced by growingthe seed of the hybrid maize variety of claim
 1. 3. A method forproducing a second maize plant comprising applying plant breedingtechniques to a first maize plant, or parts thereof, wherein said firstmaize plant is the maize plant of claim 2, and wherein application ofsaid techniques results in the production of said second maize plant. 4.The method of claim 3, further defined as producing a maize plantderived from hybrid maize variety X18A643, the method comprising thesteps of: (a) crossing said first maize plant with itself or anothermaize plant to produce seed of a subsequent generation; (b) harvestingand planting the seed of the subsequent generation to produce at leastone plant of the subsequent generation; and (c) repeating steps (a) and(b) for an additional 2-10 generations to produce a maize plant derivedfrom hybrid maize variety X18A643.
 5. The method of claim 3, furtherdefined as producing an inbred maize plant derived from hybrid maizevariety X18A643, the method comprising the steps of: (a) crossing saidfirst maize plant with an inducer variety to produce haploid seed; and(b) doubling the haploid seed to produce an inbred maize plant derivedfrom hybrid maize variety X18A643.
 6. A converted seed of hybrid maizevariety X18A643 further comprising a locus conversion, wherein said seedis produced by crossing a first plant of variety PH8JV with a secondplant of variety PH17C4; wherein representative seed of said varietiesPH8JV and PH17C4 have been deposited under ATCC Accession NumberPTA-7761 and PTA-120279, respectively; wherein at least one of saidvarieties PH8JV and PH17C4 further comprises a locus conversion; andwherein the converted hybrid seed produces a plant having the locusconversion and otherwise having essentially the same phenotypic traitslisted in Table 1 as hybrid maize variety X18A643 when grown under thesame environmental conditions.
 7. The seed of claim 6, wherein the locusconversion confers a trait selected from the group consisting of malesterility, site-specific recombination, abiotic stress tolerance,altered phosphorus, altered antioxidants, altered fatty acids, alteredessential amino acids, altered carbohydrates, herbicide tolerance,insect resistance and disease resistance.
 8. A plant or plant partproduced by growing the seed of the maize hybrid variety of claim
 6. 9.A method for producing a second maize plant comprising applying plantbreeding techniques to a first maize plant, or parts thereof, whereinsaid first maize plant is the maize plant of claim 8, and whereinapplication of said techniques results in the production of said secondmaize plant.
 10. The method of claim 9, further defined as producing amaize plant derived from hybrid maize variety X18A643, the methodcomprising the steps of: (a) crossing said first maize plant with itselfor another maize plant to produce seed of a subsequent generation; (b)harvesting and planting the seed of the subsequent generation to produceat least one plant of the subsequent generation; and repeating steps (a)and (b) for an additional 2-10 generations to produce a maize plantderived from hybrid maize variety X18A643.
 11. The method of claim 9,further defined as producing an inbred maize plant derived from hybridmaize variety X18A643, the method comprising the steps of: (a) crossingsaid first maize plant with an inducer variety to produce haploid seed;and (b) doubling the haploid seed to produce an inbred maize plantderived from hybrid maize variety X18A643.